AusCERT - ESB-2000.398 -- Cisco Security Advisory -- Cisco Catalyst SSH protocol mismatch vulnerability

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ESB-2000.398 -- Cisco Security Advisory -- Cisco Catalyst SSH protocol mismatch vulnerability
Date: 15 December 2000
References: ESB-2004.0234

Click here for printable version
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              AUSCERT External Security Bulletin Redistribution
                             
                   ESB-2000.398 -- Cisco Security Advisory
             Cisco Catalyst SSH protocol mismatch vulnerability
                              15 December 2000

===========================================================================

	AusCERT Security Bulletin Summary
	---------------------------------

Product:                Catalyst
Vendor:                 Cisco
Platform:               Cisco Catalyst 6000, 5000, 4000 Switches
                        versions 6.1(1), 6.1(1a) and 6.1(1b)
Impact:                 Denial of Service
Access Required:        Remote

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Cisco Catalyst SSH protocol mismatch vulnerability

Revision 1.0
For release 2000 December 13 10:00 AM US/Pacific (UTC+0700)

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

Summary

Non-SSH connection attempts to an enabled SSH service on a Cisco Catalyst
6000, 5000, or 4000 switch might cause a "protocol mismatch" error,
resulting in a supervisor engine failure.  The supervisor engine failure
causes the switch to fail to pass traffic and  reboots the switch. This
problem is resolved in software release 6.1(1c).  Due to a very limited
number of customer downloads, Cisco has chosen to notify affected customers
directly.

This vulnerability has been assigned Cisco bug ID CSCds85763.

The full text of this advisory can be viewed at:
http://www.cisco.com/warp/public/707/catalyst-ssh-protocolmismatch-pub.shtml.

Affected Products

Catalyst 6000, 5000, 4000 images with SSH support.  Version 6.1(1),
6.1(1a), 6.1(1b) with 3 DES features only.

Only the following images are affected:

    cat4000-k9.6-1-1.bin
    cat5000-sup3cvk9.6-1-1a.bin
    cat5000-sup3k9.6-1-1.bin
    cat5000-supgk9.6-1-1.bin
    cat6000-sup2cvk9.6-1-1b.bin
    cat6000-sup2k9.6-1-1b.bin
    cat6000-supcvk9.6-1-1b.bin
    cat6000-supk9.6-1-1b.bin

Cisco IOS 12.1 SSH implementation is not affected by this vulnerability.
No other Cisco devices are affected.

Details

 Non SSH protocol connection attempts to the SSH service cause a "protocol
mismatch" error, which causes a switch to reload.  SSH is not enabled by
default, and must be configured by the administrator.

To verify if your image is affected, run the command "show version".  If
the image filename is listed above, and you have enabled SSH, you are
affected by this vulnerability and should upgrade to a fixed version
immediately.

Impact

This vulnerability enables a Denial of Service attack on the Catalyst
switch.

Software Versions and Fixes

This defect is resolved in Cisco Catalyst version 6.1(1c).  Previous
affected versions will be deferred, and will no longer be available for
customer download.

Getting Fixed Software

Cisco is offering free software upgrades to remedy this vulnerability for
all affected customers.

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

Customers without contracts should get their 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

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

The workaround for this vulnerability is to disable SSH service.  For most
customers using this image, SSH support is necessary, so the recommended
action is to upgrade to a fixed version.

Exploitation and Public Announcements

This vulnerability was reported to Cisco by a customer who discovered the
issue during routine networking tests.  There has been no public
disclosure, and no reports of malicious activity with regard to this
vulnerability.

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.


Distribution

This notice will be posted on Cisco's Worldwide Web site at
http://www.cisco.com/warp/public/707/catalyst-ssh-protocolmismatch-pub.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  recipients:

   * cust-security-announce@cisco.com
   * Various internal Cisco mailing lists
   * Specifically affected customers

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 1.0 For public release 13-DEC-2000 10:00 AM US/Pacific
             (UTC+0700)

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
Web site at
http://www.cisco.com/warp/public/707/sec_incident_response.shtml. This
includes instructions for press inquiries regarding Cisco security notices.

  ------------------------------------------------------------------------
This notice is copyright 2000 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, including
all date and version information.

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

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Internet Email: auscert@auscert.org.au
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