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Cisco Security Advisory: Cisco IOS Software Border Gateway Protocol 4-Byte Autonomous System Number Vulnerabilities
From: Cisco Systems Product Security Incident Response Team <psirt () cisco com>
Date: Wed, 29 Jul 2009 15:00:00 -0000

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Cisco Security Advisory: Cisco IOS Software Border Gateway Protocol
                         4-Byte Autonomous System Number
                         Vulnerabilities

Advisory ID: cisco-sa-20090729-bgp

http://www.cisco.com/warp/public/707/cisco-sa-20090729-bgp.shtml

Revision: 1.0
=========

For Public Release 2009 July 29 1600 UTC (GMT)

Summary
=======

Recent versions of Cisco IOS Software support RFC4893 ("BGP Support
for Four-octet AS Number Space") and contain two remote denial of
service (DoS) vulnerabilities when handling specific Border Gateway
Protocol (BGP) updates.

These vulnerabilities affect only devices running Cisco IOS Software
with support for four-octet AS number space (here after referred to as
4-byte AS number) and BGP routing configured.

The first vulnerability could cause an affected device to reload when
processing a BGP update that contains autonomous system (AS) path
segments made up of more than one thousand autonomous systems.

The second vulnerability could cause an affected device to reload when
the affected device processes a malformed BGP update that has been
crafted to trigger the issue.

Cisco has released free software updates to address these
vulnerabilities.

No workarounds are available for the first vulnerability.

A workaround is available for the second vulnerability.

This advisory is posted at the following link:
http://www.cisco.com/warp/public/707/cisco-sa-20090729-bgp.shtml

Affected Products
=================

Vulnerable Products
+------------------

These vulnerabilities affect only devices running Cisco IOS and 
Cisco IOS XE Software (here after both referred to as simply Cisco
IOS) with support for RFC4893 and that have been configured for 
BGP routing.

The software table in the section "Software Versions and Fixes" of
this advisory indicates all affected Cisco IOS Software versions that
have support for RFC4893 and are affected by this vulnerability.

A Cisco IOS software version that has support for RFC4893 will allow
configuration of AS numbers using 4 Bytes. The following example
identifies a Cisco device that has 4 byte AS number support:

    Router#configure terminal
    Enter configuration commands, one per line.  End with CNTL/Z.
    Router(config)#router bgp ?
      <1-65535>    Autonomous system number
      <1.0-XX.YY>  4 Octets Autonomous system number

    Or:

    Router#configure terminal
    Enter configuration commands, one per line.  End with CNTL/Z.
    Router(config)#router bgp ?
      <1-4294967295>  Autonomous system number
      <1.0-XX.YY>     Autonomous system number

The following example identifies a Cisco device that has 2 byte AS
number support:

    Router#configure terminal
    Enter configuration commands, one per line.  End with CNTL/Z.
    Router(config)#router bgp ?
      <1-65535>  Autonomous system number

A router that is running the BGP process will contain a line in the
configuration that defines the autonomous system number (AS number),
which can be seen by issuing the command line interface (CLI) command
"show running-config".

The canonical textual representation of four byte AS Numbers is
standardized by the IETF through RFC5396 (Textual Representation of
Autonomous System (AS) Numbers). Two major ways for textual
representation have been defined as ASDOT and ASPLAIN. Cisco IOS
routers support both textual representations of AS numbers. For
further information about textual representation of four byte AS
numbers in Cisco IOS Software consult the document "Explaining 4-Byte
Autonomous System (AS) ASPLAIN and ASDOT Notation for Cisco IOS" at
the following link:
http://www.cisco.com/en/US/prod/collateral/iosswrel/ps6537/ps6554/ps6599/white_paper_c11_516829.html
   
Cisco IOS Software with support for RFC4893 is affected by both
vulnerabilities if BGP routing is configured using either ASPLAIN or
ASDOT notation.

The following example identifies a Cisco device that is configured
for BGP using ASPLAIN notation:

    router bgp 65536

The following example identifies a Cisco device that is configured
for BGP using ASDOT notation:

    router bgp 1.0

To determine the Cisco IOS Software release that is running on a
Cisco product, administrators can log in to the device and issue the
show version command to display the system banner. The system banner
confirms that the device is running Cisco IOS Software by displaying
text similar to "Cisco Internetwork Operating System Software" or
"Cisco IOS Software." The image name displays in parentheses,
followed by "Version" and the Cisco IOS Software release name. Other
Cisco devices do not have the show version command or may provide
different output.

The following example identifies a Cisco product that is running
Cisco IOS Software Release 12.3(26) with an installed image name of
C2500-IS-L:

    Router#show version
    Cisco Internetwork Operating System Software
    IOS (tm) 2500 Software (C2500-IS-L), Version 12.3(26), RELEASE SOFTWARE (fc2)
    Technical Support: http://www.cisco.com/techsupport
    Copyright (c) 1986-2008 by cisco Systems, Inc.   
    Compiled Mon 17-Mar-08 14:39 by dchih


    !--- output truncated


The following example identifies a Cisco product that is running
Cisco IOS Software Release 12.4(20)T with an installed image name of
C1841-ADVENTERPRISEK9-M:

    Router#show version
    Cisco IOS Software, 1841 Software (C1841-ADVENTERPRISEK9-M), Version 12.4(20)T, RELEASE SOFTWARE (fc3)
    Technical Support: http://www.cisco.com/techsupport
    Copyright (c) 1986-2008 by Cisco Systems, Inc.
    Compiled Thu 10-Jul-08 20:25 by prod_rel_team


    !--- output truncated


Additional information about Cisco IOS Software release naming
conventions is available in "White Paper: Cisco IOS Reference Guide"
at the following link: http://www.cisco.com/warp/public/620/1.html

Products Confirmed Not Vulnerable  
+--------------------------------

The following Cisco products are confirmed not vulnerable:

  * Cisco IOS Software not explicitly mentioned in this Advisory
  * Cisco IOS XR Software
  * Cisco IOS NX-OS

No other Cisco products are currently known to be affected by this
vulnerability.

Details     
=======   

RFC4271 has defined an AS number as a two-octet entity in BGP. 
RFC4893 has defined an AS number as a four-octet entity in BGP.

The first vulnerability could cause an affected device to reload when
processing a BGP update that contains AS path segments made up of more
than one thousand autonomous systems. If an affected 4-byte AS number
BGP speaker receives a BGP update from a 2-byte AS number BGP speaker
that contains AS path segments made up of more than one thousand
autonomous systems, the device may crash with memory corruption, and
the error "%%Software-forced reload" will be displayed.

The following three conditions are required for successful
exploitation of this vulnerability:

  * Affected Cisco IOS Software device is a 4-byte AS number BGP
    speaker
  * BGP peering neighbor is a 2-byte AS number BGP speaker
  * BGP peering neighbor is capable of sending a BGP update with a
    series of greater than one thousand AS numbers

    Note: Note: Cisco IOS, Cisco IOS XE, Cisco NX-OS and Cisco IOS XR
    Software, as a 2 byte AS number BGP speaker send BGP updates with
    a maximum of 255 AS numbers.

This vulnerability is documented in Cisco Bug ID CSCsy86021 and has
been assigned Common Vulnerabilities and Exposures (CVE) ID
CVE-2009-1168.

The second vulnerability could cause an affected device to reload when
the affected device processes a malformed BGP update that has been
crafted to trigger the issue. The following three conditions are
required for successful exploitation of this vulnerability:

  * Affected Cisco IOS Software device is a 4-byte AS number BGP
    speaker
  * BGP peering neighbor is a 2-byte AS number BGP speaker
  * BGP peering neighbor is capable of sending a non-RFC compliant
    crafted BGP update message

This vulnerability is documented in Cisco Bug ID CSCta33973 and has
been assigned Common Vulnerabilities and Exposures (CVE) ID 
CVE-2009-2049.

Further information regarding Cisco support for 4-byte AS number is
available in "Cisco IOS BGP 4-Byte ASN Support" at the following
link: 
http://www.cisco.com/en/US/prod/collateral/iosswrel/ps6537/ps6554/ps6599/data_sheet_C78-521821.html

Vulnerability Scoring Details      
=============================
   
Cisco has provided scores for the vulnerabilities in this advisory
based on the Common Vulnerability Scoring System (CVSS). The CVSS
scoring in this Security Advisory is done in accordance with CVSS
version 2.0.

CVSS is a standards-based scoring method that conveys vulnerability
severity and helps determine urgency and priority of response.

Cisco has provided a base and temporal score. Customers can then
compute environmental scores to assist in determining the impact of
the vulnerability in individual networks.

Cisco has provided an FAQ to answer additional questions regarding
CVSS at

http://www.cisco.com/web/about/security/intelligence/cvss-qandas.html

Cisco has also provided a CVSS calculator to help compute the
environmental impact for individual networks at

http://intellishield.cisco.com/security/alertmanager/cvss


CSCsy86021: Cisco IOS Software BGP Long AS-path Vulnerability

CVSS Base Score - 7.1

Access Vector           Network
Access Complexity       Medium
Authentication          None
Confidentiality Impact  None
Availability Impact     Complete

CVSS Temporal Score - 6.7
Exploitability          Functional
Remediation Level       Official-Fix
Report Confidence       Confirmed
 
   
CSCta33973: Cisco IOS Software Crafted BGP Update Message Vulnerability
 
CVSS Base Score - 5.4

Access Vector           Network
Access Complexity       High
Authentication          None
Confidentiality Impact  None
Availability Impact     Complete

CVSS Temporal Score - 4.5
Exploitability          Functional
Remediation Level       Official-Fix
Report Confidence       Confirmed
   
Impact
======     
   
Successful exploitation of the vulnerabilities described in this
document may result in a reload of the device. The issue could result
in repeated exploitation to cause an extended DoS condition.
   
Software Versions and Fixes
===========================

When considering software upgrades, also consult
http://www.cisco.com/go/psirt and any subsequent advisories to
determine exposure and a complete upgrade solution.

In all cases, customers should exercise caution to be certain the
devices to be upgraded contain sufficient memory and that current
hardware and software configurations will continue to be supported
properly by the new release. If the information is not clear, contact
the Cisco Technical Assistance Center (TAC) or your contracted
maintenance provider for assistance.

Each row of the Cisco IOS software table (below) names a Cisco IOS
release train. If a given release train is vulnerable, then the
earliest possible releases that contain the fix (along with the
anticipated date of availability for each, if applicable) are listed
in the "First Fixed Release" column of the table. The "Recommended
Release" column indicates the releases which have fixes for all the
published vulnerabilities at the time of this Advisory. A device
running a release in the given train that is earlier than the release
in a specific column (less than the First Fixed Release) is known to
be vulnerable. Cisco recommends upgrading to a release equal to or
later than the release in the "Recommended Releases" column of the
table.
   
+-------------------------------------------------------------------+
|  Major   |             Availability of Repaired Releases          |
| Release  |                                                        |
|----------+--------------------------------------------------------|
| Affected |                                           |Recommended |
|12.0-Based|           First Fixed Release             |  Release   |
| Releases |                                           |            |
|----------+-------------------------------------------+------------|
|12.0      |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.0DA    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.0DB    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.0DC    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|          |Releases up to and including 12.0(32)S11   |            |
|          |are not vulnerable; first fixed in         |            |
|12.0S     |12.0(32)S14;                               |            |
|          |                                           |            |
|          |Releases up to and including 12.0(33)S2 are|            |
|          |not vulnerable; first fixed in 12.0(33)S5  |            |
|----------+-------------------------------------------+------------|
|12.0SC    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.0SL    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.0SP    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.0ST    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.0SX    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.0SY    |Releases up to and including 12.0(32)SY7   |12.0(32)SY10|
|          |are not vulnerable; first fixed in         |            |
|          |12.0(32)SY9a.                              |            |
|----------+-------------------------------------------+------------|
|12.0SZ    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.0T     |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.0W     |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.0WC    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.0WT    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.0WX    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.0XA    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.0XB    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.0XC    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.0XD    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.0XE    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.0XF    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.0XG    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.0XH    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.0XI    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.0XJ    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.0XK    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.0XL    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.0XM    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.0XN    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.0XQ    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.0XR    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.0XS    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.0XT    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.0XV    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.0XW    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
| Affected |                                           |Recommended |
|12.1-Based|            First Fixed Release            |  Release   |
| Releases |                                           |            |
|-------------------------------------------------------------------|
|             There are no affected 12.1 based releases             |
|-------------------------------------------------------------------|
| Affected |                                           |Recommended |
|12.2-Based|            First Fixed Release            |  Release   |
| Releases |                                           |            |
|----------+-------------------------------------------+------------|
|12.2      |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2B     |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2BC    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2BW    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2BX    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2BY    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2BZ    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2CX    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2CY    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2CZ    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2DA    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2DD    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2DX    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2EW    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2EWA   |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2EX    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2EY    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2EZ    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2FX    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2FY    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2FZ    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2IRA   |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2IRB   |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2IRC   |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2IXA   |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2IXB   |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2IXC   |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2IXD   |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2IXE   |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2IXF   |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2IXG   |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2IXH   |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2JA    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2JK    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2MB    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2MC    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2S     |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2SB    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2SBC   |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2SCA   |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2SCB   |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2SE    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2SEA   |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2SEB   |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2SEC   |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2SED   |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2SEE   |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2SEF   |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2SEG   |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2SG    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2SGA   |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2SL    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2SM    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2SO    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2SQ    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2SRA   |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2SRB   |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2SRC   |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2SRD   |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2STE   |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2SU    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2SV    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2SVA   |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2SVC   |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2SVD   |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2SVE   |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2SW    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2SX    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2SXA   |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2SXB   |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2SXD   |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2SXE   |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2SXF   |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2SXH   |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|          |Releases up to and including 12.2(33)SXI   |            |
|12.2SXI   |are not vulnerable; CSCsy86021 first fixed |            |
|          |in 12.2(33)SXI2; CSCta33973 first fixed in |            |
|          |12.2(33)SXI3                               |            |
|----------+-------------------------------------------+------------|
|12.2SY    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2SZ    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2T     |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2TPC   |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2XA    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2XB    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2XC    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2XD    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2XE    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2XF    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2XG    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2XH    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2XI    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2XJ    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2XK    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2XL    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2XM    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2XN    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2XNA   |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2XNB   |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2XNC   |12.2(33)XNC2                               |            |
|----------+-------------------------------------------+------------|
|12.2XND   |12.2(33)XND1; available 25th August 2009   |            |
|----------+-------------------------------------------+------------|
|12.2XO    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2XQ    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2XR    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2XS    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2XT    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2XU    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2XV    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2XW    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2YA    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2YB    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2YC    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2YD    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2YE    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2YF    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2YG    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2YH    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2YJ    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2YK    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2YL    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2YM    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2YN    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2YO    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2YP    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2YQ    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2YR    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2YS    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2YT    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2YU    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2YV    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2YW    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2YX    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2YY    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2YZ    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2ZA    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2ZB    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2ZC    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2ZD    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2ZE    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2ZF    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2ZG    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2ZH    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2ZJ    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2ZL    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2ZM    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2ZP    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2ZU    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2ZX    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2ZY    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.2ZYA   |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
| Affected |                                           |Recommended |
|12.3-Based|            First Fixed Release            |  Release   |
| Releases |                                           |            |
|-------------------------------------------------------------------|
|             There are no affected 12.3 based releases             |
|-------------------------------------------------------------------|
| Affected |                                           |Recommended |
|12.4-Based|            First Fixed Release            |  Release   |
| Releases |                                           |            |
|----------+-------------------------------------------+------------|
|12.4      |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.4JA    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.4JDA   |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.4JDC   |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.4JDD   |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.4JK    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.4JL    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.4JMA   |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.4JMB   |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.4JX    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.4MD    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.4MDA   |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.4MR    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.4SW    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|          |Releases up to 12.4(24)T are not           |            |
|12.4T     |vulnerable; first fixed in 12.4(24)T2      |            |
|          |available on 23-Oct-2009                   |            |
|----------+-------------------------------------------+------------|
|12.4XA    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.4XB    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.4XC    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.4XD    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.4XE    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.4XF    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.4XG    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.4XJ    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.4XK    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.4XL    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.4XM    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.4XN    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.4XP    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.4XQ    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.4XR    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.4XT    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.4XV    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.4XW    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.4XY    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.4XZ    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.4YA    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.4YB    |Not Vulnerable                             |            |
|----------+-------------------------------------------+------------|
|12.4YD    |Not Vulnerable                             |            |
+-------------------------------------------------------------------+

Cisco IOS XE Release Table
+-------------------------

+-------------------------------------------------------------------+
|  Major   |              Availability of Repaired Releases         |
| Release  |                                                        |
|----------+--------------------------------------------------------|
| Affected |                                                        |
|   2.1    | There are no affected 2.1 based releases               |
| Releases |                                                        |
|----------+--------------------------------------------------------|
| Affected |                                                        |
|   2.2    | There are no affected 2.2 based releases               |
| Releases |                                                        |
|----------+--------------------------------------------------------|
| Affected | Releases up to and including 2.3.1t are vulnerable;    |
|   2.3    | First fixed in 2.3.2                                   |
| Releases |                                                        |
|----------+--------------------------------------------------------+
| Affected | Releases up to and including 2.4.0 are vulnerable;     |
|   2.4    | First fixed in 2.4.1, available 25th August 2009       |
| Releases |                                                        |
+----------+--------------------------------------------------------+
   
Workarounds
===========

For the first vulnerability, there are no workarounds on the affected
device. Neighbors could be configured to discard routes that have
more than one thousand AS numbers in the AS-path segments. This
configuration will help prevent the further propagation of BGP
updates with the AS path segments made up of greater than one
thousand AS numbers.

Note: Configuring "bgp maxas-limit [value]" on the affected device
does not mitigate this vulnerability.

For the second vulnerability, configuring "bgp maxas-limit [value]"
on the affected device does mitigate this vulnerability. Cisco is
recommends using a conservative value of 100 to mitigate this
vulnerability.

Consult the document "Protecting Border Gateway Protocol for the
Enterprise" at the following link for additional best practices on
protecting BGP infrastructures: 
http://www.cisco.com/web/about/security/intelligence/protecting_bgp.html

Obtaining Fixed Software
========================

Cisco has released free software updates that address these
vulnerabilities. Prior to deploying software, customers should
consult their maintenance provider or check the software for feature
set compatibility and known issues specific to their environment.

Customers may only install and expect support for the feature sets
they have purchased. By installing, downloading, accessing or
otherwise using such software upgrades, customers agree to be bound
by the terms of Cisco's software license terms found at 
http://www.cisco.com/en/US/docs/general/warranty/English/EU1KEN_.html
or as otherwise set forth at Cisco.com Downloads at
http://www.cisco.com/public/sw-center/sw-usingswc.shtml

Do not contact psirt () cisco com or security-alert () cisco com for
software upgrades.

Customers with Service Contracts
+-------------------------------

Customers with contracts should obtain upgraded software through
their regular update channels. For most customers, this means that
upgrades should be obtained through the Software Center on Cisco's
worldwide website at http://www.cisco.com.

Customers using Third Party Support Organizations
+------------------------------------------------

Customers whose Cisco products are provided or maintained through
prior or existing agreements with third-party support organizations,
such as Cisco Partners, authorized resellers, or service providers
should contact that support organization for guidance and assistance
with the appropriate course of action in regards to this advisory.

The effectiveness of any workaround or fix is dependent on specific
customer situations, such as product mix, network topology, traffic
behavior, and organizational mission. Due to the variety of affected
products and releases, customers should consult with their service
provider or support organization to ensure any applied workaround or
fix is the most appropriate for use in the intended network before it
is deployed.

Customers without Service Contracts
+----------------------------------

Customers who purchase direct from Cisco but do not hold a Cisco
service contract, and customers who purchase through third-party
vendors but are unsuccessful in obtaining fixed software through
their point of sale should acquire upgrades by contacting the Cisco
Technical Assistance Center (TAC). TAC contacts are as follows.

  * +1 800 553 2447 (toll free from within North America)
  * +1 408 526 7209 (toll call from anywhere in the world)
  * e-mail: tac () cisco com

Customers should have their product serial number available and be
prepared to give the URL of this notice as evidence of entitlement to
a free upgrade. Free upgrades for non-contract customers must be
requested through the TAC.

Refer to 
http://www.cisco.com/en/US/support/tsd_cisco_worldwide_contacts.html
for additional TAC contact information, including localized 
telephone numbers, and instructions and e-mail addresses for use
in various languages.

Exploitation and Public Announcements
=====================================

The Cisco PSIRT is not aware of malicious exploitation of either of
these vulnerabilities, although we are aware of some customers who
have seen the first vulnerability triggered within their
infrastructures. Further investigation of those incidents seems to
indicate that the vulnerability has been accidentally triggered.

These vulnerabilities were discovered via internal product testing.

Status of this Notice: FINAL
============================

This information is Cisco Highly Confidential - Do not redistribute.

THIS IS A DRAFT VERSION OF A SECURITY NOTICE THAT CONTAINS UNRELEASED
INFORMATION ABOUT CISCO PRODUCTS. DISTRIBUTION WITHIN CISCO IS
LIMITED TO PERSONNEL WITH A NEED TO KNOW. THIS DRAFT MAY CONTAIN
ERRORS OR OMIT IMPORTANT INFORMATION.

THIS DOCUMENT IS PROVIDED ON AN "AS IS" BASIS AND DOES NOT IMPLY ANY
KIND OF GUARANTEE OR WARRANTY, INCLUDING THE WARRANTIES OF
MERCHANTABILITY OR FITNESS FOR A PARTICULAR USE. YOUR USE OF THE
INFORMATION ON THE DOCUMENT OR MATERIALS LINKED FROM THE DOCUMENT IS
AT YOUR OWN RISK. CISCO RESERVES THE RIGHT TO CHANGE OR UPDATE THIS
DOCUMENT AT ANY TIME.

Distribution
============

This advisory is posted on Cisco's worldwide website at:
   
http://www.cisco.com/warp/public/707/cisco-sa-20090729-bgp.shtml
   
In addition to worldwide web posting, a text version of this notice
is clear-signed with the Cisco PSIRT PGP key and is posted to the
following e-mail and Usenet news recipients.

  * cust-security-announce () cisco com
  * first-bulletins () lists first org
  * bugtraq () securityfocus com
  * vulnwatch () vulnwatch org
  * cisco () spot colorado edu
  * cisco-nsp () puck nether net
  * full-disclosure () lists grok org uk
  * comp.dcom.sys.cisco () newsgate cisco com

Future updates of this advisory, if any, will be placed on Cisco's
worldwide website, but may or may not be actively announced on
mailing lists or newsgroups. Users concerned about this problem are
encouraged to check the above URL for any updates.

Revision History
================

+-------------------------------------------------------------------+
| Revision 1.0   | 2009-July-29 1600    | Initial public release    |
+-------------------------------------------------------------------+

Cisco Security Procedures
=========================

Complete information on reporting security vulnerabilities in Cisco
products, obtaining assistance with security incidents, and
registering to receive security information from Cisco, is available
on Cisco's worldwide website at 
http://www.cisco.com/en/US/products/products_security_vulnerability_policy.html 
This includes instructions for press inquiries regarding Cisco 
security notices.  All Cisco security advisories are available at 
http://www.cisco.com/go/psirt


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