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Cisco Security Advisory: Multiple Vulnerabilities in Cisco Firewall Services Module
From: Cisco Systems Product Security Incident Response Team <psirt () cisco com>
Date: Wed, 04 Aug 2010 11:45:00 -0400

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Cisco Security Advisory: Multiple Vulnerabilities in Cisco Firewall
Services Module

Advisory ID: cisco-sa-20100804-fwsm

Revision 1.0

For Public Release 2010 August 04 1600 UTC (GMT)

+---------------------------------------------------------------------

Summary
=======

Multiple vulnerabilities exist in the Cisco Firewall Services Module
(FWSM) for the Cisco Catalyst 6500 Series Switches and Cisco 7600
Series Routers that may cause the Cisco FWSM to reload after
processing crafted SunRPC or certain TCP packets. Repeated
exploitation could result in a sustained DoS condition.

Cisco has released free software updates that address these
vulnerabilities. Workarounds are available for the vulnerabilities
disclosed in this advisory.

Note:  These vulnerabilities are independent of each other. A device
may be affected by one vulnerability and not affected by another.

This advisory is posted at:

http://www.cisco.com/warp/public/707/cisco-sa-20100804-fwsm.shtml

Note:  The Cisco ASA 5500 Series Adaptive Security Appliances are
affected by the SunRPC inspection vulnerabilities described in this
advisory. A separate Cisco Security Advisory has been published to
disclose this and other vulnerabilities that affect the Cisco ASA
5500 Series Adaptive Security Appliances. The advisory is available
at:

http://www.cisco.com/warp/public/707/cisco-sa-20100804-asa.shtml

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

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

The Cisco Firewall Services Module (FWSM) for the Cisco Catalyst 6500
Series Switches and Cisco 7600 Series Routers is affected by multiple
vulnerabilities. Affected versions of Cisco FWSM Software vary
depending on the specific vulnerability.

SunRPC Inspection Denial of Service Vulnerabilities
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Cisco FWSM Software version 3.x and 4.x are affected by these
vulnerabilities only if SunRPC inspection is enabled. SunRPC
inspection is enabled by default.

To check if SunRPC inspection is enabled, use the "show service-policy
| include sunrpc" command and confirm that the command returns output,
as shown in the following example:

    fwsm#show service-policy | include sunrpc
          Inspect: sunrpc , packet 0, drop 0, reset-drop 0

Alternatively, a device that has SunRPC inspection enabled has a
configuration similar to the following:

    class-map inspection_default
     match default-inspection-traffic
    !
    policy-map global_policy
     class inspection_default
      ...
      inspect sunrpc
      ...
    !
    service-policy global_policy global

Note:  The Cisco ASA 5500 Series Adaptive Security Appliances are
affected by the SunRPC inspection vulnerabilities described in this
advisory. A separate Cisco Security Advisory has been published to
disclose this and other vulnerabilities that affect the Cisco ASA
5500 Series Adaptive Security Appliances. The advisory is available
at:

http://www.cisco.com/warp/public/707/cisco-sa-20100804-asa.shtml

TCP Denial of Service Vulnerability
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Cisco FWSM Software version 3.x and 4.x are affected by this
vulnerability when configured in multi-mode (with virtual firewalls)
and with any of the following features:

  * ASDM Administrative Access
  * Telnet
  * SSH

To verify if the FWSM is running in multiple mode, use the "show mode"
command, as shown in the following example:

    FWSM(config)#show mode
    Security context mode: multiple
    The flash mode is the SAME as the running mode.

The following commands are used to enable the HTTPS server and allow
only hosts on the inside interface with an address in the 192.168.1.0
/24 network to create ASDM, SSH or Telnet connections:

    asa(config)# http server enable
    asa(config)# http 192.168.1.0 255.255.255.0 inside
    asa(config)# telnet 192.168.1.0 255.255.255.0 inside
    asa(config)# ssh 192.168.1.0 255.255.255.0 inside

Determining Software Versions
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

To determine the version of Cisco FWSM Software that is running,
issue the "show module" command from Cisco IOS Software or Cisco
Catalyst Operating System Software to identify what modules and sub
modules are installed on the system.

The following example shows a system with a Cisco FWSM (WS-SVC-FWM-1)
installed in slot 2:

    switch>show module
    Mod Ports Card Type                              Model              Serial No.
    --- ----- -------------------------------------- ------------------ -----------
      1   16  SFM-capable 16 port 1000mb GBIC        WS-X6516-GBIC      SAL06334NS9
      2    6  Firewall Module                        WS-SVC-FWM-1       SAD10360485
      3    8  Intrusion Detection System             WS-SVC-IDSM-2      SAD0932089Z
      4    4  SLB Application Processor Complex      WS-X6066-SLB-APC   SAD093004BD
      5    2  Supervisor Engine 720 (Active)         WS-SUP720-3B       SAL0934888E
    
    Mod MAC addresses                       Hw    Fw           Sw           Status
    --- ---------------------------------- ------ ------------ ------------ -------
      1  0009.11e3.ade8 to 0009.11e3.adf7   5.1   6.3(1)       8.5(0.46)RFW Ok
      2  0018.ba41.5092 to 0018.ba41.5099   4.0   7.2(1)       3.2(2)10     Ok
      3  0014.a90c.9956 to 0014.a90c.995d   5.0   7.2(1)       5.1(6)E1     Ok
      4  0014.a90c.66e6 to 0014.a90c.66ed   1.7                4.2(3)       Ok
      5  0013.c42e.7fe0 to 0013.c42e.7fe3   4.4   8.1(3)       12.2(18)SXF1 Ok
    
    [...]

After locating the correct slot, issue the "show module <slot number>"
command to identify the software version that is running, as shown in
the following example:

    switch>show module 2
    Mod Ports Card Type                              Model              Serial No.
    --- ----- -------------------------------------- ------------------ -----------
      2    6  Firewall Module                        WS-SVC-FWM-1       SAD10360485
    
    Mod MAC addresses                       Hw    Fw           Sw           Status
    --- ---------------------------------- ------ ------------ ------------ -------
      2  0018.ba41.5092 to 0018.ba41.5099   4.0   7.2(1)       3.2(2)10     Ok
    
    [...]

The preceding example shows that the FWSM is running software version
3.2(2)10 as indicated by the column under "Sw."

Note:  Recent versions of Cisco IOS Software will show the software
version of each module in the output from the "show module" command;
therefore, executing the "show module <slot number>" command is not
necessary.

If a Virtual Switching System (VSS) is used to allow two physical
Cisco Catalyst 6500 Series Switches to operate as a single logical
virtual switch, the "show module switch all" command can display the
software version of all FWSMs that belong to switch 1 and switch 2.
The output from this command will be similar to the output from the 
"show module <slot number>" but will include module information for the
modules in each switch in the VSS.

Alternatively, version information can be obtained directly from the
FWSM through the show version command, as shown in the following
example:

    FWSM> show version
    FWSM Firewall Version 3.2(2)10 
    [...]

Customers who use the Cisco Adaptive Security Device Manager (ASDM)
to manage their devices can find the version of the software
displayed in the table in the login window or in the upper left
corner of the ASDM window. The version notation is similar to the
following example.

    FWSM Version: 3.2(2)10

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

With the exception of Cisco ASA 5500 Series Adaptive Security
Appliances, no other Cisco products are currently known to be
affected by these vulnerabilities.

Details
=======

The Cisco FWSM is a high-speed, integrated firewall module for Cisco
Catalyst 6500 Series Switches and Cisco 7600 Series Routers. The FWSM
offers firewall services with stateful packet filtering and deep
packet inspection.

SunRPC Inspection Denial of Service Vulnerabilities
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

The Cisco FWSM is affected by three vulnerabilities that may cause
the device to reload during the processing of different crafted
SunRPC messages when SunRPC inspection is enabled.

Note:  These vulnerabilities are only triggered by transit traffic;
traffic that is destined to the device does not trigger these
vulnerabilities.

These vulnerabilities are documented in Cisco bug IDs CSCte61710, 
CSCte61622, and CSCte61662; and have been assigned Common
Vulnerabilities and Exposures (CVE) IDs CVE-2010-2818, CVE-2010-2819,
and CVE-2010-2820, respectively.

TCP Denial of Service Vulnerability
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

You can partition a single FWSM into multiple virtual devices, known
as security contexts. Each context has its own security policy,
interfaces, and administrators. Multiple contexts are similar to
multiple standalone devices. Many features are supported in multiple
context mode, which includes routing tables, firewall features, and
management.

Cisco FWSM is affected by a denial of service vulnerability that
could allow an unauthenticated attacker to cause a reload when
sending a series of TCP packets. The Cisco FWSM is only affected by
this vulnerability when is configured in multi-mode (with virtual
firewalls) and configured to accept Telnet, SSH or ASDM connections.

Note:  A TCP three-way handshake is needed to exploit this
vulnerability. This vulnerability is only triggered by traffic that
is destined to the affected device; transit traffic does not trigger
this vulnerability.

This vulnerability is documented in Cisco bug ID CSCtg68694 
and has been assigned Common Vulnerabilities and Exposures (CVE) ID
CVE-2010-2821.

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

CSCte61710, CSCte61622, CSCte61662 - Passthrough traffic crashes FWSM
with SunRPC inspection

CVSS Base Score - 7.8

Access Vector           - Network
Access Complexity       - Low
Authentication          - None
Confidentiality Impact  - None
Integrity Impact        - None
Availability Impact     - Complete

CVSS Temporal Score - 6.4

Exploitability          - Functional
Remediation Level       - Official-Fix
Report Confidence       - Confirmed

CSCtg68694 - FWSM may crash with certain TCP sessions in multiple mode

CVSS Base Score - 7.1                     

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

CVSS Temporal Score - 6.4

Exploitability          - Functional
Remediation Level       - Official-Fix
Report Confidence       - Confirmed

Impact
======

Successful exploitation of all the vulnerabilities described in this
security advisory may cause a reload of the affected appliance.
Repeated exploitation could result in a sustained 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.

+-------------------------------------------------------------------+
|                                            |  Major  |   First    |
|               Vulnerability                | Release |   Fixed    |
|                                            |         |  Release   |
|--------------------------------------------+---------+------------|
|                                            | 3.1     | 3.1(17.2)  |
|                                            |---------+------------|
| SunRPC Inspection Denial of Service        | 3.2     | 3.2(16.1)  |
| Vulnerabilities (CSCte61710, CSCte61622,   |---------+------------|
| and CSCte61662)                            | 4.0     | 4.0(10.1)  |
|                                            |---------+------------|
|                                            | 4.1     | 4.1(1.1)   |
|--------------------------------------------+---------+------------|
|                                            | 3.1     | Not        |
|                                            |         | vulnerable |
|                                            |---------+------------|
| TCP Denial of Service Vulnerability        | 3.2     | 3.2(17.2)  |
| (CSCtg68694)                               |---------+------------|
|                                            | 4.0     | 4.0(11.1)  |
|                                            |---------+------------|
|                                            | 4.1     | 4.1(1.2)   |
+-------------------------------------------------------------------+

Recommended Releases
~~~~~~~~~~~~~~~~~~~~

The following table lists all recommended releases. These recommended
releases contain the fixes for all vulnerabilities in this advisory.
Cisco recommends upgrading to a release that is equal to or later
than these recommended releases.

+-------------------------------------------------------------------+
|       Major Release       |          Recommended Release          |
|---------------------------+---------------------------------------|
| 3.1                       | 3.1(18)                               |
|---------------------------+---------------------------------------|
| 3.2                       | 3.2(18)                               |
|---------------------------+---------------------------------------|
| 4.0                       | 4.0(12)                               |
|---------------------------+---------------------------------------|
| 4.1                       | 4.1(2)                                |
+-------------------------------------------------------------------+

Software Download
~~~~~~~~~~~~~~~~~

Fixed Cisco FWSM Software can be downloaded from the Software Center
on Cisco.com by visiting:

http://www.cisco.com/cisco/web/download/index.html

and navigating to:

Security > Cisco Catalyst 6500 Series Firewall Services Module > Firewall Services Module (FWSM) Software

Workarounds
===========

The SunRPC inspection vulnerabilities can be mitigated by disabling
SunRPC inspection, if it is not required. Administrators can disable
SunRPC inspection by issuing the "no inspect sunrpc" command in class
configuration sub-mode within policy-map configuration.

The TCP DoS vulnerability can be mitigated by only allowing trusted
hosts to communicate with the FWSM via HTTPs, SSH, or Telnet. For
example, the following commands are used to enable the HTTPS server
and allow only hosts on the inside interface with an address in the
192.168.1.0/24 network to create ASDM, SSH or Telnet connections:

    asa(config)# http server enable
    asa(config)# http 192.168.1.0 255.255.255.0 inside
    asa(config)# telnet 192.168.1.0 255.255.255.0 inside
    asa(config)# ssh 192.168.1.0 255.255.255.0 inside

Additional mitigation techniques that can be deployed on Cisco
devices within the network are available in the Cisco Applied
Mitigation Bulletin companion document for this advisory:

http://www.cisco.com/warp/public/707/cisco-amb-20100804-fwsm.shtml

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 any public announcements or malicious
use of the vulnerability described in this advisory.

These vulnerabilities were found during the troubleshooting of
customer service requests and internal testing.

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

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.

A stand-alone copy or Paraphrase of the text of this document that
omits the distribution URL in the following section is an
uncontrolled copy, and may lack important information or contain
factual errors.

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

This advisory is posted on Cisco's worldwide website at:

http://www.cisco.com/warp/public/707/cisco-sa-20100804-fwsm.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 |                | Initial   |
| 1.0      | 2010-August-04 | 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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