Hash: SHA1

             AUSCERT External Security Bulletin Redistribution

                         ESB-2007.0137 -- [Cisco]
 Cisco Catalyst 6000, 6500 and Cisco 7600 Series MPLS Packet Vulnerability
                               1 March 2007


        AusCERT Security Bulletin Summary

Product:              Catalyst 6500 with IOS Software Modularity
                      Catalyst 6000, 6500 and 7600 with Hybrid Mode MSFC
Publisher:            Cisco Systems
Operating System:     IOS
Impact:               Denial of Service
Access:               Remote/Unauthenticated

Original Bulletin:    

Comment: Note that the affected systems may be vulnerable to these MPLS
         packets even if not configured for MPLS.

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Hash: SHA1

Cisco Security Advisory: Cisco Catalyst 6000, 6500 and Cisco 7600
Series MPLS Packet Vulnerability

Advisory ID: cisco-sa-20070228-mpls

Revision 1.0

For Public Release 2007 February 28 

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


Cisco Catalyst 6500 series systems that are running certain versions
of Cisco Internetwork Operating System (IOS) are vulnerable to an
attack from a Multi Protocol Label Switching (MPLS) packet. Only the
systems that are running in Hybrid Mode (Catalyst OS (CatOS) software
on the Supervisor Engine and IOS Software on the Multilayer Switch
Feature Card (MSFC)) or running with Cisco IOS Software Modularity
are affected.

MPLS packets can only be sent from the local network segment.

This advisory is posted at 

Affected Products

Vulnerable Products

The following products are affected by this vulnerability:

  * Cisco Catalyst 6500 systems that run 12.2(18)SXF4 with Cisco IOS
    Software Modularity are affected.

    Images that support Cisco IOS Software Modularity have a "-vz"
    suffix in their image name.

    The following is a conclusive list of all image names that are
    running with Cisco IOS Software Modularity and are affected by
    this vulnerability.

      + s72033-adventerprisek9_wan-vz.122-18.SXF4.bin
      + s72033-advipservicesk9_wan-vz.122-18.SXF4.bin
      + s72033-entservicesk9_wan-vz.122-18.SXF4.bin
      + s72033-ipservices_wan-vz.122-18.SXF4.bin
      + s72033-ipservicesk9_wan-vz.122-18.SXF4.bin
      + s72033-ipservicesk9-vz.122-18.SXF4.bin

  * Cisco Catalyst 6000, 6500 and Cisco 7600 series systems with an
    MSFC2 or MSFC3 that run in Hybrid Mode are affected.

    In Hybrid Mode, Catalyst OS (CatOS) software runs on the
    Supervisor Engine and IOS runs on the MSFC. It is different from
    the Native Mode in which IOS runs both on the Supervisor Engine
    and MSFC.

    This vulnerability affects MSFC2, MSFC2a and MSFC3 that run
    certain images in Hybrid mode.

    In Hybrid Mode, IOS images that run on MSFC start with "c6msfc2",
    "c6msfc2a" or "c6msfc3". Several image names that run on MSFC in
    hybrid mode are provided below for reference:

      + c6msfc2a-adventerprisek9_wan-mz.122-18.SXF
      + c6msfc3-jsv-mz.122-14.SX2

Products Confirmed Not Vulnerable

  * Systems that are running in Native Mode without Cisco IOS
    Software Modularity are not affected.
  * Systems without an MSFC2, MSFC2a or MSFC3 are not affected.

No other Cisco products are known to be affected by this


Cisco IOS Software Modularity combines subsystems into individual
processes and enhances the Cisco IOS Software memory architecture to
provide process-level fault isolation and subsystem "In Service
Software Upgrade" (ISSU) capability. These enhancements are delivered
in Cisco IOS Software for the Catalyst 6500 Series Supervisor Engine
720 and Supervisor Engine 32. Cisco IOS Software Modularity was first
delivered as an option in a Cisco IOS Software Release 12.2(18)SXF4.
More information on Modular IOS can be found at the following URL:


Not all 12.2(18)SXF4 images support Modular IOS. Only the images with
a "-vz" in the image name support Modular IOS and are affected by
this vulnerability. A conclusive list of all affected image names
that support Cisco IOS Software Modularity is provided in the
Affected Products section.

In Hybrid Mode, a CatOS image is used as the system software to run
the Supervisor Engine on the Catalyst systems. If an MSFC is
installed, a separate IOS Software image is used in order to run the
MSFC. CatOS provides the Layer 2 (L2) switching functionality. The
Cisco IOS on the MSFC provides the Layer 3 (L3) routing
functionality. It differs from the Native Mode, in which a single
Cisco IOS Software image is used as the system software to run both
the Supervisor Engine and MSFC on the Catalyst systems. IOS software
that runs on MSFC in Hybrid Mode is also affected by this
vulnerability. More information about the differences between Hybrid
and Native Modes can be found at the following URL:


MPLS packets received by a Route Processor (MSFC) Layer 3 interface
can potentially trigger this vulnerability. The system in question
does not need to be configured for MPLS to be vulnerable. MPLS
packets can only be sent from the local network segment, limiting the
scope of the exploitation.

This issue is documented in bug IDs CSCsd37415 ( registered customers
only) and CSCef90002 ( registered customers only) .

Vulnerability Scoring Details

Cisco is providing scores for the vulnerabilities in this advisory
based on the Common Vulnerability Scoring System (CVSS). Cisco will
provide a base and temporal score. Customers can then compute
environmental scores to assist in determining the impact of the
vulnerability in individual networks.

Cisco PSIRT will set the bias in all cases to normal. Customers are
encouraged to apply the bias parameter when determining the
environmental impact of a particular vulnerability.

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

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

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

CSCsd37415 - RP crashed on sending MPLS packet to a interface

CVSS Base Score: 3.3
- - - Access Vector: Remote
- - - Access Complexity: Low
- - - Authentication: Not Required
- - - Confidentiality Impact: None
- - - Integrity Impact: None
- - - Availability Impact: Complete
- - - Impact Bias: Normal

CVSS Temporal Score: 2.7
- - - Exploitability: Functional
- - - Remediation Level: Official Fix
- - - Report Confidence: Confirmed

CSCef90002 - MSFC crashed due to corrupted program counter

CVSS Base Score: 3.3
- - - Access Vector: Remote
- - - Access Complexity: Low
- - - Authentication: Not Required
- - - Confidentiality Impact: None
- - - Integrity Impact: None
- - - Availability Impact: Complete
- - - Impact Bias: Normal

CVSS Temporal Score: 2.7
- - - Exploitability: Functional
- - - Remediation Level: Official Fix
- - - Report Confidence: Confirmed


Successful exploitation of the vulnerability may result in the reload
of the system on systems that are running with Cisco IOS Software
Modularity and the reload of MSFC on systems that are running in
Hybrid Mode.

Repeated exploitation may lead to a denial of service condition.

Software Version 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 that
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) 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 (the "First Fixed Release") and the
anticipated date of availability for each are listed in the "Rebuild"
and "Maintenance" columns. 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. The release
should be upgraded at least to the indicated release or a later
version (greater than or equal to the First Fixed Release label).

For more information on the terms "Rebuild" and "Maintenance,"
consult the following URL: 

|         |    Availability of Fixed    |
| Trains  |          Releases           |
|         |-----------------------------|
|         |    Rebuild    | Maintenance |
| 12.1E   | Not vulnerable              |
| 12.2SXA | Vulnerable. Migrate to 12.2 |
|         | (17d)SXB5 or later          |
| 12.2SXB | 12.2(17d)SXB5 |             |
| 12.2SXD | 12.2(18)SXD3  |             |
| 12.2SXE | Not vulnerable              |
| 12.2SXF | 12.2(18)SXF5  |             |
| (*)     |               |             |

* Only 12.2(18)SXF4 with IOS Software Modularity is affected. 12.2SXF
releases that run in Hybrid Mode are not affected. Please see the
Affected Products section for more information.

A special patch for 12.2(18)SXF4 with Cisco IOS Software Modularity
is also available.

Patch Name: MA0045

Image Name: s72033-AMA0045-patch.122-18.SXF4

The above patch can be downloaded from the Cisco IOS Software
Modularity Patch Navigator at 


There are no workarounds for this vulnerability.

Additional mitigations that can be deployed on Cisco devices within
the network are available in the Cisco Applied Intelligence companion
document for this advisory: 

Obtaining Fixed Software

Cisco will make free software available to address this vulnerability
for affected customers. This advisory will be updated as fixed
software becomes available. Prior to deploying software, customers
should consult their maintenance provider or check the software for
feature set compatibility and known issues specific to their

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/public/sw-license-agreement.html, or as 
otherwise set forth at Cisco.com Downloads at 

Do not contact either "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 agreement 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 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)
  * e-mail: tac@cisco.com

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

Refer to 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.

Exploitation and Public Announcements

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

This vulnerability was reported by a customer.

Status of this Notice:FINAL


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.


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


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-teams@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      | 2007-February-28 | 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 
This includes instructions for press inquiries regarding Cisco 
security notices. All Cisco security advisories are available 
at http://www.cisco.com/go/psirt.
Version: GnuPG v1.4.6 (GNU/Linux)


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