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Cisco Security Advisory: Scanning for SSH Can Cause a Crash
From: Cisco Systems Product Security Incident Response Team <psirt () cisco com>
Date: Wed, 27 Jun 2002 16:00:00 GMT

-----BEGIN PGP SIGNED MESSAGE-----

Security Advisory: Scanning for SSH Can Cause a Crash

Revision 1.0

For Public Release 2002 June 27 16:00 (UTC 0000)

- ---------------------------------------------------------------------------

Summary
=======
While fixing vulnerabilities mentioned in the Cisco Security Advisory:
Multiple SSH Vulnerabilities (http://www.cisco.com/warp/public/707/
SSH-multiple-pub.html) we inadvertently introduced an instability in some
products. When an attacker tries to exploit the vulnerability VU#945216
(described in the CERT/CC Vulnerability Note at http://www.kb.cert.org/vuls
/id/945216) the SSH module will consume too much of the processor's time,
effectively causing a DoS. In some cases the device will reboot. In order
to be exposed SSH must be enabled on the device.

Affected product lines are:

  * All devices running Cisco IOSĀ® Software supporting SSH. This includes
    routers and switches running Cisco IOS Software.
   
  * Catalyst 6000 switches running CatOS.
   
  * Cisco PIX Firewall.
   
  * Cisco 11000 Content Service Switch family.

No other Cisco product is vulnerable. It is possible to mitigate this
vulnerability by preventing, or having control over, the SSH traffic.

This advisory is available at http://www.cisco.com/warp/public/707/
SSH-scanning.shtml.

Affected Products
=================
  * All devices running Cisco IOS Software supporting SSH. This includes
    routers and switches running Cisco IOS Software.
   
  * Catalyst 6000 switches running CatOS.
   
  * Cisco PIX Firewall.
   
  * Cisco 11000 Content Service Switch family.

+--------------------------------------------------+
|  Product Category  |      Vulnerability ID       |
|--------------------+-----------------------------|
| IOS                | CSCdw33027                  |
|--------------------+-----------------------------|
| PIX                | CSCdw29965                  |
|--------------------+-----------------------------|
| VPN 3000           | Not affected                |
|--------------------+-----------------------------|
| Catalyst 6000      | CSCdv85279 and CSCdw59394   |
|--------------------+-----------------------------|
| CSS 11000          | CSCdx59197                  |
+--------------------------------------------------+

All software releases listed in the http://www.cisco.com/warp/public/707/
SSH-multiple-pub.html (Cisco Security Advisory: Multiple SSH
Vulnerabilities), including all subsequent software releases that contain
the patches addressed by that advisory are vulnerable.

All software that does not contain fixes for the issues listed in the
previous SSH advisory are not vulnerable to the issue described in this
advisory. However, falling back to a previous software release will leave
you exposed to the vulnerabilities described in the previous advisory and
you will lose any additional features or functionalities introduced in the
newer releases.

No other Cisco products are affected.

Details
=======
While fixing the vulnerabilities listed in http://www.cisco.com/warp/public
/707/SSH-multiple-pub.html (Cisco Security Advisory: Multiple SSH
Vulnerabilities) an instability is introduced in some products. When
exposed to an overly large packet, the SSH process will consume a large
portion of the processor's instruction cycles, effectively causing a DoS.
The capability to create such a packet is available in publicly available
exploit code. In some cases this availability attack may result in a reboot
of the device. In order to be exposed SSH must be enabled on the device.

The vulnerability in question is named CRC-32 Check in the http://
www.cisco.com/warp/public/707/SSH-multiple-pub.html. It is also marked as
VU#945216 and described in the CERT/CC Vulnerability Note at http://
www.kb.cert.org/vuls/id/945216.

Impact
======
By repeatedly exploiting this vulnerability an attacker can cause a denial
of service, though Cisco products remain unaffected to the exploits that
are trying to exploit vulnerabilities listed in http://www.cisco.com/warp/
public/707/SSH-multiple-pub.html.

Software Versions and Fixes
===========================
For CSS 11000 family, the vulnerability is fixed in the following software
releases.

+--------------------------------------------------+
| WebNS  | R5.00.045 or later (available now)      |
|        | 5.10.1.01 available July 2002           |
+--------------------------------------------------+

For Catalyst 6000 switches, the vulnerability is fixed in the following
CatOS releases. This table lists the first fixed release.

+--------------------------------------------------+
| CatOS  | 6.3(3.6), 7.1(0.94), 7.2(0.14)PEN       |
+--------------------------------------------------+

Each row of the table describes a release train and the platforms or
products for which it is intended. If a given release train is vulnerable,
then the earliest possible releases that contain the fix and the
anticipated date of availability for each are listed in the "Rebuild",
"Interim", and "Maintenance" columns. A device running any release in the
given train that is earlier than the release in a specific column (less
than the earliest fixed release) is known to be vulnerable, and it should
be upgraded at least to the indicated release or a later version (greater
than the earliest fixed release label).

When selecting a release, keep in mind the following definitions:

    Maintenance
        Most heavily tested and highly recommended release of any label in
        a given row of the table.
       
    Rebuild
        Constructed from the previous maintenance or major release in the
        same train, it contains the fix for a specific defect. Although it
        receives less testing, it contains only the minimal changes
        necessary to effect the repair.
       
    Interim
        Built at regular intervals between maintenance releases and
        receives less testing. Interims should be selected only if there is
        no other suitable release that addresses the vulnerability. Interim
        images should be upgraded to the next available maintenance release
        as soon as possible. Interim releases are not available through
        manufacturing, and usually they are not available for customer
        download from CCO without prior arrangement with the Cisco
        Technical Assistance Center (TAC).
       
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 TAC for
assistance as shown in the following section.

More information on Cisco IOS software release names and abbreviations is
available at http://www.cisco.com/warp/public/620/1.html.

For PIX Firewall software, use the following table to determine affected
and fixed software releases.

+---------------------------------------------------------+
|       | Description |                                   |
| Train | of Image or |  Availability of Fixed Releases*  |
|       |  Platform   |                                   |
|---------------------+-----------------------------------|
| 5.x-based Releases  | Rebuild | Interim** | Maintenance |
|---------------------+---------+-----------+-------------|
|       | General     |         |           |             |
|       | Deployment  |         |           |             |
|       | (GD) for    |         | 5.2(6)202 |             |
|  5.2  | Classic,    |         | Available | 5.2(7)      |
|       | 10000, 506, |         | through   |             |
|       | 506E, 510,  |         | TAC       |             |
|       | 515, 515E,  |         |           |             |
|       | 520 and 525 |         |           |             |
|-------+-------------+---------+-----------+-------------|
|       | Early       |         |           |             |
|       | Deployment  |         |           |             |
|       | (ED) for    |         | 5.3(2)205 |             |
|       | Classic,    |         | Available |             |
|  5.3  | 10000, 506, |         | through   | 5.3(3)      |
|       | 506E, 510,  |         | TAC       |             |
|       | 515, 515E,  |         |           |             |
|       | 520, 525    |         |           |             |
|       | and 535     |         |           |             |
|---------------------+---------+-----------+-------------|
| 6.x-based Releases  | Rebuild | Interim** | Maintenance |
|---------------------+---------+-----------+-------------|
|       | Early       |         |           |             |
|       | Deployment  |         | 6.0(1)106 |             |
|       | (ED) for    |         | Available |             |
|  6.0  | 501, 506,   |         | through   | 6.0(2)      |
|       | 506E, 515,  |         | TAC       |             |
|       | 515E, 520,  |         |           |             |
|       | 525 and 535 |         |           |             |
|-------+-------------+---------+-----------+-------------|
|       | Early       |         |           |             |
|       | Deployment  |         | 6.1(1)105 |             |
|       | (ED) for    |         | Available |             |
|  6.1  | 501, 506,   |         | through   | 6.1(2)      |
|       | 506E, 515,  |         | TAC       |             |
|       | 515E, 520,  |         |           |             |
|       | 525 and 535 |         |           |             |
|-------+-------------+---------+-----------+-------------|
|       | Early       |         |           |             |
|       | Deployment  |         | 6.2(0)222 |             |
|       | (ED) for    |         | Available |             |
|  6.2  | 501, 506,   |         | through   | 6.2(1)      |
|       | 506E, 515,  |         | TAC       |             |
|       | 515E, 520,  |         |           |             |
|       | 525 and 535 |         |           |             |
+---------------------------------------------------------+

For Cisco IOS software, use the following table to determine affected and
fixed software releases. This table always lists the first fixed release,
which is not necessarily the recommended release for your particular
environment.

+-----------------------------------------------------------------------+
| Train  | Description of Image  |   Availability of Fixed Releases*    |
|        |      or Platform      |                                      |
|--------------------------------+--------------------------------------|
|      12.0-based Releases       |  Rebuild   | Interim |  Maintenance  |
|                                |            |   **    |               |
|--------------------------------+------------+---------+---------------|
| 12.0S  | Core/ISP support:     | 12.0(17)S4 | 12.0    | 12.0(21)S     |
|        | GSR, RSP, c7200       |            | (20.4)S |               |
|--------+-----------------------+------------+---------+---------------|
|        | Core/ISP support:     | 12.0(20)   | 12.0    |               |
| 12.0SP | GSR, RSP, c7200       | SP2        | (20.4)  |               |
|        |                       |            | SP      |               |
|--------+-----------------------+------------+---------+---------------|
|        | Core/ISP support:     | 12.0(17)   | 12.0    |               |
| 12.0ST | GSR, RSP, c7200       | ST5        | (20.3)  | 12.0(21)S     |
|        |                       |            | ST2     |               |
|--------+-----------------------+--------------------------------------|
|        | Early Deployment      | Not Scheduled                        |
| 12.0XB |Release                |--------------------------------------|
|        |                       | Migrate to 12.1(1)T or later         |
|--------+-----------------------+--------------------------------------|
|        | Early Deployment      | Not Scheduled                        |
| 12.0XM |Release                |--------------------------------------|
|        |                       | Migrate to 12.1(3)T or later         |
|--------+-----------------------+--------------------------------------|
|        | Early Deployment      | Not Scheduled                        |
| 12.0XV |Release                |--------------------------------------|
|        |                       | Migrate to 12.1(2)T or later         |
|--------------------------------+--------------------------------------|
|      12.1-based Releases       |  Rebuild   | Interim |  Maintenance  |
|                                |            |   **    |               |
|--------------------------------+--------------------------------------|
|        | General deployment    |                                      |
|  12.1  | release for all       | SSH not supported                    |
|        | platforms             |                                      |
|--------+-----------------------+--------------------------------------|
|        | Core/ISP support:     |            | 12.1    |               |
| 12.1E  | GSR, RSP, c7200,      | 12.1(8b)E8 | (10.5)E | 12.1(11b)E    |
|        | Catalyst 6000         |            |         |               |
|--------+-----------------------+------------+---------+---------------|
|        | Early Deployment      |            | 12.1    |               |
| 12.1EC | Release               |            | (10.5)  | 12.1(12c)EC   |
|        |                       |            | EC      |               |
|--------+-----------------------+--------------------------------------|
|  12.1  | Early Deployment      | Not Scheduled                        |
| (1)EX  |Release                |--------------------------------------|
|        |                       | Migrate to 12.1(3)T or later         |
|--------+-----------------------+--------------------------------------|
|  12.1  |                       | Not Scheduled                        |
| (5c)EX |Catalyst 6000 support  |--------------------------------------|
|        |                       | Migrate to 12.1(6)EX or later        |
|--------+-----------------------+--------------------------------------|
|  12.1  |                       | Not Scheduled                        |
| (8a)EX |12.1E based XED        |--------------------------------------|
|        |                       | Migrate to 12.1(11)E or later        |
|--------+-----------------------+--------------------------------------|
|  12.1  | Early Deployment      | Not Scheduled                        |
| (9)EX  |Release                |--------------------------------------|
|        |                       | Migrate to 12.1(10)EX or later       |
|--------+-----------------------+--------------------------------------|
|        | Early Deployment(ED): | Not Scheduled                        |
|        | VPN, Distributed      |                                      |
| 12.1T  |Director, various      |--------------------------------------|
|        | platforms             | Migrate to 12.2 or later             |
|        |                       |                                      |
|--------+-----------------------+--------------------------------------|
|        | Early Deployment      | Not Scheduled                        |
| 12.1XB |Release                |--------------------------------------|
|        |                       | Migrate to 12.1(5)YB or later        |
|--------+-----------------------+--------------------------------------|
|        | Early Deployment      | Not Scheduled                        |
| 12.1XC |(ED): limited          |--------------------------------------|
|        | platforms             | Migrate to 12.2 or later             |
|--------+-----------------------+--------------------------------------|
|        | Early Deployment      | 12.1(2)XF6 |         | Not planned,  |
| 12.1XF | (ED): 811 and 813     | Release    |         | migrate to    |
|        | (c800 images)         | date to be |         | 12.1(5)T or   |
|        |                       | determined |         | later         |
|--------+-----------------------+------------+---------+---------------|
|        | Early Deployment      | 12.1(3)XG7 |         | Not planned,  |
| 12.1XG | (ED): 800, 805, 820,  | Release    |         | migrate to    |
|        | and 1600              | date to be |         | 12.2(1)T or   |
|        |                       | determined |         | later         |
|--------+-----------------------+--------------------------------------|
|        | Early Deployment      | Not Scheduled                        |
| 12.1XH |(ED): limited          |--------------------------------------|
|        | platforms             | Migrate to 12.2 or later             |
|--------+-----------------------+--------------------------------------|
|        | Early Deployment      | Not Scheduled                        |
| 12.1XI |(ED): limited          |--------------------------------------|
|        | platforms             | Migrate to 12.2 or later             |
|--------+-----------------------+--------------------------------------|
|        | Early Deployment      | Not Scheduled                        |
| 12.1XJ |(ED): limited          |--------------------------------------|
|        | platforms             | Migrate to 12.2(2)T or later         |
|--------+-----------------------+--------------------------------------|
|        | Early Deployment      | Not Scheduled                        |
| 12.1XL |(ED): limited          |--------------------------------------|
|        | platforms             | Migrate to 12.2 or later             |
|--------+-----------------------+--------------------------------------|
|        |                       |            |         | Not planned,  |
| 12.1XM | Short-lived early     | 12.1(5)XM7 |         | migrate to    |
|        | deployment release    |            |         | 12.2(1)T or   |
|        |                       |            |         | later         |
|--------+-----------------------+--------------------------------------|
|        | Short-lived early     | Not Scheduled                        |
| 12.1XP |deployment release     |--------------------------------------|
|        |                       | Migrate to 12.2(2)T or later         |
|--------+-----------------------+--------------------------------------|
|        | Short-lived early     | Not Scheduled                        |
| 12.1XQ |deployment release     |--------------------------------------|
|        |                       | Migrate to 12.2(2)XB or later        |
|--------+-----------------------+--------------------------------------|
|        | Early Deployment      | Not Scheduled                        |
| 12.1XT |(ED): 1700 series      |--------------------------------------|
|        |                       | Migrate to 12.2(2)T or later         |
|--------+-----------------------+--------------------------------------|
|        | Early Deployment      | Not Scheduled                        |
| 12.1XU |(ED): limited          |--------------------------------------|
|        | platforms             | Migrate to 12.2T or later            |
|--------+-----------------------+--------------------------------------|
|        |                       | 12.1(5)YB6 |         | Not planned,  |
| 12.1YB | Short-lived early     | Release    |         | migrate to    |
|        | deployment release    | date to be |         | 12.2(2)T or   |
|        |                       | determined |         | later         |
|--------+-----------------------+------------+---------+---------------|
|        |                       | 12.1(5)YC3 |         | Not planned,  |
| 12.1YC | Short-lived early     | Release    |         | migrate to    |
|        | deployment release    | date to be |         | 12.2(4)T or   |
|        |                       | determined |         | later         |
|--------+-----------------------+--------------------------------------|
|        | Short-lived early     | Not Scheduled                        |
| 12.1YD |deployment release     |--------------------------------------|
|        |                       | Migrate to 12.2(8)T or later         |
|--------+-----------------------+--------------------------------------|
|        | Short-lived early     | Not Scheduled                        |
| 12.1YE |deployment release     |--------------------------------------|
|        |                       | Migrate to 12.1(5)YI or later        |
|--------+-----------------------+--------------------------------------|
|        | Short-lived early     | Not Scheduled                        |
| 12.1YF |deployment release     |--------------------------------------|
|        |                       | Migrate to 12.2(2)XN or later        |
|--------+-----------------------+--------------------------------------|
|        | Short-lived early     | Not Scheduled                        |
| 12.1YI |deployment release     |--------------------------------------|
|        |                       | Migrate to 12.2(2)YC or later        |
|--------------------------------+--------------------------------------|
|      12.2-based Releases       |  Rebuild   | Interim |  Maintenance  |
|                                |            |   **    |               |
|--------------------------------+------------+---------+---------------|
|        | General deployment    |            | 12.2    |               |
|  12.2  | release for all       | 12.2(6b)   | (7.4)   | 12.2(7)       |
|        | platforms             |            |         |               |
|--------+-----------------------+------------+---------+---------------|
| 12.2B  | Early Deployment      | 12.2(4)B3  | 12.2    |               |
|        | Broadband Release     |            | (7.6)B  |               |
|--------+-----------------------+------------+---------+---------------|
|        | Early Deployment      |            |         |               |
| 12.2BC | Broadband Release     | 12.2(8)BC1 |         |               |
|        | uBR7000 and uBR10000  |            |         |               |
|--------+-----------------------+------------+---------+---------------|
| 12.2DA | Early Deployment      | 12.2(6.8a) |         | 12.2(7)DA     |
|        | Release: xDSL         | DA         |         |               |
|--------+-----------------------+--------------------------------------|
|        | Specific Technology   | Not Scheduled                        |
| 12.2DD |Early Deployment       |--------------------------------------|
|        | release for 7200 and  | Migrate to 12.2(4)B1 or later        |
|--------+-----------------------+--------------------------------------|
| 12.2S  | SPLOB                 |            | 12.2    |               |
|        |                       |            | (7.4)S  |               |
|--------+-----------------------+------------+---------+---------------|
|        | General deployment    |            | 12.2    |               |
| 12.2T  | release for all       |            | (7.4)T  | 12.2(8)T      |
|        | platforms             |            |         |               |
|--------+-----------------------+--------------------------------------|
|        | Early Deployment      | Not Scheduled                        |
| 12.2XA |Release                |--------------------------------------|
|        |                       | Migrate to 12.2(4)T or 12.2(2)XB     |
|--------+-----------------------+--------------------------------------|
|        | Early Deployment      | 12.2(2)XB4 |         |               |
| 12.2XB | Release               | Available  |         |               |
|        |                       | 2002-July  |         |               |
|--------+-----------------------+------------+---------+---------------|
|        |                       |            |         | Not planned,  |
| 12.2XD | ICS7750, 820, soho70  | 12.2(1)XD4 |         | migrate to    |
|        |                       |            |         | 12.2(8)T or   |
|        |                       |            |         | later         |
|--------+-----------------------+------------+---------+---------------|
|        |                       |            |         | Not planned,  |
| 12.2XE | 806, 820, soho78      | 12.2(1)XE3 |         | migrate to    |
|        |                       |            |         | 12.2(8)T or   |
|        |                       |            |         | later         |
|--------+-----------------------+--------------------------------------|
|        | DOCSYS support,       | Not Scheduled                        |
| 12.2XF |uBR7100, uBR7200,      |--------------------------------------|
|        | uBR10000              | Migrate to 12.2(4)BC1                |
|--------+-----------------------+--------------------------------------|
|        |                       | Not Scheduled                        |
| 12.2XG |IAD2400/2600/3600      |--------------------------------------|
|        |                       | Migrate to 12.2(8)T                  |
|--------+-----------------------+--------------------------------------|
|        | 1700, 800, 820,       |            |         | Not planned,  |
| 12.2XH | soho70                | 12.2(2)XH3 |         | migrate to    |
|        |                       |            |         | 12.2(8)T      |
|--------+-----------------------+------------+---------+---------------|
|        | Early Deployment      |            |         | Not planned,  |
| 12.2XI | Release 820/SOHO      | 12.2(2)XI2 |         | migrate to    |
|        |                       |            |         | 12.2(12)T     |
|--------+-----------------------+--------------------------------------|
|        |                       | Not Scheduled                        |
| 12.2XJ |1700                   |--------------------------------------|
|        |                       | Migrate to 12.2(4)YB                 |
|--------+-----------------------+--------------------------------------|
|        | Early Deployment      |            |         | Not planned,  |
| 12.2XK | Release 820/SOHO      | 12.2(2)XK3 |         | migrate to    |
|        |                       |            |         | 12.2(12)T     |
|--------+-----------------------+------------+---------+---------------|
|        | 1700, 820, 800,       | 12.2(4)XL5 |         | Not planned,  |
| 12.2XL | SOHO70                | Available  |         | migrate to    |
|        |                       | 2002-June  |         | 12.2(12)T     |
|--------+-----------------------+------------+---------+---------------|
| 12.2XM | Early Deployment      | 12.2(4)XM4 |         |               |
|        | Release               |            |         |               |
|--------+-----------------------+--------------------------------------|
|        | Early Deployment      | Not Scheduled                        |
| 12.2XN |Release for enhanced   |--------------------------------------|
|        | MGCP support,         | Upgrade recommended to a release yet |
|        | selected platforms    | to be determined                     |
|--------+-----------------------+--------------------------------------|
|        |                       | Not Scheduled                        |
| 12.2XQ |1720, 1750, 1752       |--------------------------------------|
|        |                       | Migrate to 12.2(4)YB or later        |
|--------+-----------------------+--------------------------------------|
|        | Short-lived early     | Not Scheduled                        |
| 12.2XR |deployment release     |--------------------------------------|
|        |                       | Migrate to 12.2(4)XR or later        |
|--------+-----------------------+--------------------------------------|
|        | Short-lived early     | Not Scheduled                        |
| 12.2XS |deployment release     |--------------------------------------|
|        |                       | Migrate to 12.2(6) or later          |
|--------+-----------------------+--------------------------------------|
|        | Short-lived early     | Not Scheduled                        |
| 12.2XT |deployment release     |--------------------------------------|
|        |                       | Migrate to 12.2(8)T or later         |
|--------+-----------------------+--------------------------------------|
|        | Short-lived early     | Not Scheduled                        |
| 12.2XW |deployment release     |--------------------------------------|
|        |                       | Migrate to 12.2(4)YB or later        |
|--------+-----------------------+--------------------------------------|
| 12.2YA | Early Deployment      | 12.2(4)YA2 |         |               |
|        | Release               |            |         |               |
|--------+-----------------------+--------------------------------------|
|        |                       | Not Scheduled                        |
| 12.2YB |Short-lived early      |--------------------------------------|
|        | deployment release    | Upgrade recommended to yet to be     |
|        |                       | determined release                   |
|--------+-----------------------+--------------------------------------|
|        | Short-lived early     | Not Scheduled                        |
| 12.2YC |deployment release     |--------------------------------------|
|        |                       | Migrate to 12.2(13)T or later        |
|--------+-----------------------+--------------------------------------|
|        | Broadband suport for  | Not Scheduled                        |
| 12.2YD |7200                   |--------------------------------------|
|        |                       | Migrate to 12.2(8)B or later         |
|--------+-----------------------+--------------------------------------|
|        |                       | Not Scheduled                        |
| 12.2YF |Short-lived early      |--------------------------------------|
|        | deployment release    | Upgrade recommended to yet to be     |
|        |                       | determined release                   |
|--------+-----------------------+--------------------------------------|
| 12.2YG | Early Deployment      |            |         | 12.2(4)YG     |
|        | Release               |            |         |               |
|--------+-----------------------+------------+---------+---------------|
| 12.2YH | 1700, 8xx, soho7x,    |            |         | 12.2(4)YH     |
|        | ICS7700               |            |         |               |
|-----------------------------------------------------------------------|
|                                 Notes                                 |
|-----------------------------------------------------------------------|
| * All dates are estimates and subject to change.                      |
|                                                                       |
| ** Interim releases are subjected to less rigorous testing than       |
| regular maintenance releases, and may have serious bugs.              |
+-----------------------------------------------------------------------+

Obtaining Fixed Software
========================
Cisco is offering free software upgrades to remedy this vulnerability for
all affected customers. Customers may only install and expect support for
the feature sets they have purchased.

Customers with service contracts should obtain upgraded software through
their regular update channels to any software release containing the
feature sets they have purchased. 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 whose Cisco products are provided or maintained through prior or
existing agreement with third-party support organizations such as Cisco
Partners, authorized resellers, or service providers should contact that
support organization for assistance with the upgrade, which should be free
of charge.

Customers who purchased directly from Cisco but who do not hold a Cisco
service contract, and customers who purchase through third party vendors
but are unsuccessful at obtaining fixed software through their point of
sale, should obtain fixed software by contacting the Cisco Technical
Assistance Center (TAC). In those cases, customers may only upgrade to a
later version of the same release as indicated by the applicable row in the
Software Versions and Fixes table.

Cisco 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

See http://www.cisco.com/warp/public/687/Directory/DirTAC.shtml for
additional TAC contact information, including special localized telephone
numbers and instructions and e-mail addresses for use in various languages.

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

Please do not contact either "psirt () cisco com" or
"security-alert () cisco com" for software upgrades.

Workarounds
===========
It is possible to mitigate this vulnerability in two ways:

  * Block all SSH connections on the border on your network, or
   
  * On each individual device allow SSH connections only from the required
    IP addresses and block all others.

Blocking all SSH connections, and all other protocols that are not supposed
to come from the outside, on the network edge should be an integral part of
the network security best practice.

Exploitation and Public Announcements
=====================================
Publicly available malicous software is known to trigger this defect. 
Scanning for Unix hosts running vulnerable versions of SSH has been 
prevalent and such a scan may trigger this vulnerability.

Cisco PSIRT is aware of a few customers who experienced problems related 
to this vulnerability, however we do not have any evidence that these 
devices were targeted directly.

Status of This Notice: FINAL
============================
This is a final notice. Although Cisco cannot guarantee the accuracy of all
statements in this notice, all of the facts have been checked to the best
of our ability. Cisco does not anticipate issuing updated versions of this
notice unless there is some material change in the facts. Should there be a
significant change in the facts, Cisco may update this notice.

A standalone copy or paraphrase of the text of this security advisory that
omits the distribution URL in the following section is an uncontrolled
copy, and may lack important information or contain factual errors.

Distribution
============
This notice will be posted on Cisco's worldwide web site at http://
www.cisco.com/warp/public/707/SSH-scanning.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
  * bugtraq () securityfocus com
  * first-teams () first org (includes CERT/CC)
  * cisco () spot colorado edu
  * comp.dcom.sys.cisco
  * firewalls () lists gnac com
  * Various internal Cisco mailing lists

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

Revision History
================
+----------------------------------------------------------------------+
|Revision  |2002-June-27|Initial public release                        |
|1.0       |14:18       |                                              |
|          |GMT+0000    |                                              |
+----------------------------------------------------------------------+

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/warp/public/707/sec_incident_response.shtml
This includes instructions for press inquiries regarding Cisco security
notices. 

All Cisco Security Advisories are available at 
http:// www.cisco.com/go/psirt.

- ---------------------------------------------------------------------------

This notice is Copyright 2002 by Cisco Systems, Inc. This notice may be
redistributed freely after the release date given at the top of the text,
provided that redistributed copies are complete and unmodified, and include
all date and version information.

- ---------------------------------------------------------------------------

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