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Cisco Security Advisory: OSM Line Card Header Corruption Vulnerability

Revision 1.0 FINAL

For Public Release 2002 December 11 16:00 UTC

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Contents

Summary
Affected Products
Details
Impact
Software Versions and Fixes
Obtaining Fixed Software
Workarounds
Exploitation and Public Announcements
Status of This Advisory
Distribution
Revision History
Cisco Security Procedures

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Summary

The Optical Service Module (OSM) Line Cards installed in Catalyst 6500
or Cisco 7600 chassis, and running Cisco IOS® Software Version 12.1(8)E
and higher are vulnerable to a Denial of Service upon receiving a
specifically constructed or corrupted packet from the local network.

Cisco has provided fixed software for this problem. The vulnerability
has been assigned Cisco Bug ID CSCdy29717.

The complete advisory will be available at
http://www.cisco.com/warp/public/707/osm-lc-ios-pkt-vuln-pub.shtml.

Affected Products

The following products are affected only when they have OSM Line Cards
installed and running in conjunction with Cisco IOS Software Versions
12.1(8)E through 12.1(13.4)E:

* Catalyst 6500 with Sup2/MSFC2 modules
* Cisco 7600

No other releases of Cisco Catalyst hardware and software combinations
are affected by this vulnerability. No other Cisco products are affected
by this vulnerability.

Details

This defect was introduced by CSCdv23236 in version Cisco IOS Software
Versions 12.1(8)E. When certain malformed datagrams arrive on the
interface, the packet forwarding engine specific to this line card
rewrites the datagram in such a way that legitimate information is
overwritten resulting in the interface ceasing to receive and forward
further legitimate network traffic.

Because most networking devices typically drop the malformed datagrams,
the attack must occur from a locally attached network.

Bug ID
CSCdy29717 - Traffic forwarding stops due to packet header corruption.

Impact

This defect causes traffic forwarding to fail, resulting in a denial of
service. This can only be triggered from the local network and is not
propagated across networks by most layer 3 devices.

Software Versions and Fixes

This vulnerability is repaired in version 12.1(13.5)E, and is available
for general download in version 12.1(13)E1 and 12.1(12c)E2, and will be
available going forward in all versions supporting this hardware
combination, specifically 12.1(14)E. The 12.2S train is not affected by
this vulnerability, as this particular hardware combination is not
currently supported with the 12.2S software.

Obtaining Fixed Software

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/public/sw-center/sw-ios.shtml .

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 obtaining the free
software upgrade(s).

Customers who purchase direct 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 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)
* email: [email protected] <mailto:[email protected]> .

See http://www.cisco.com/warp/public/687/Directory/DirTAC.shtml
<http://www.cisco.com/warp/public/687/Directory/DirTAC.shtml&gt; 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
<http://www.cisco.com/warp/public/707/osm-lc-ios-pkt-vuln-pub.shtml&gt; of
this advisory 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 "[email protected]" or
"[email protected]" for software upgrades.

Workarounds

No workarounds exist for this vulnerability. Cisco recommends upgrading
to repaired versions.

Exploitation and Public Announcements

The Cisco PSIRT is not aware of any public announcements or malicious
use of the vulnerability described in this advisory.

Status of This Advisory: FINAL

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

A stand-alone 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 advisory will be posted on Cisco's worldwide website at
http://www.cisco.com/warp/public/707/osm-lc-ios-pkt-vuln-pub.shtml
<http://www.cisco.com/warp/public/707/osm-lc-ios-pkt-vuln-pub.shtml&gt;. In
addition to worldwide web posting, a text version of this advisory is
clear-signed with the Cisco PSIRT PGP key and is posted to the following
e-mail and Usenet news recipients:

* [email protected]
* [email protected]
* [email protected]
* [email protected] (includes CERT/CC)
* [email protected]
* [email protected]
* comp.dcom.sys.cisco
* Various internal Cisco mailing lists

Future updates of this advisory, if any, will be placed on Cisco's
worldwide web Users concerned about this problem are encouraged to check
the URL given above for any updates.

Revision History

Revision 1.0 2002-Dec-11 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/warp/public/707/sec_incident_response.shtml
<http://www.cisco.com/warp/public/707/sec_incident_response.shtml&gt;. This
includes instructions for press inquiries regarding Cisco security
advisories. All Cisco Security Advisories are available at
http://www.cisco.com/go/psirt <http://www.cisco.com/go/psirt&gt;.

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This advisory is Copyright 2002 by Cisco Systems, Inc. This advisory 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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