Cisco Security Advisory: Cisco IOS MPLS Forwarding Infrastructure Denial of Service Vulnerability

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Advisory ID: cisco-sa-20080924-mfi

http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20080924-mfi

Revision 1.1

For Public Release 2008 September 24 16:00 UTC (GMT)

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

Summary

Cisco IOS Software Multi Protocol Label Switching (MPLS) Forwarding Infrastructure (MFI) is vulnerable to a Denial of Service (DoS) attack from specially crafted packets. Only the MFI is affected by this vulnerability. Older Label Forwarding Information Base (LFIB) implementation, which is replaced by MFI, is not affected.

Cisco has released free software updates that address this vulnerability.

This advisory is posted at http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20080924-mfi.

Note: The September 24, 2008 IOS Advisory bundled publication includes twelve Security Advisories. Eleven of the advisories address vulnerabilities in Cisco's IOS software, and one advisory addresses vulnerabilities in Cisco Unified Communications Manager. Each Advisory lists the releases that correct the vulnerability described in the Advisory.

Individual publication links are listed below:

Affected Products

Devices that run Cisco IOS software (including those that support Cisco IOS Software Modularity) and support MFI are affected if they are configured for MPLS.

Vulnerable Products

A device that runs Cisco IOS software and supports MFI will have mfi_ios in the output of the show subsys command. The following example shows output from a device that supports MFI:

Router#show subsys name mfi_ios
             Class         Version 
mfi_ios      Protocol    1.000.001
Router#

The following example shows output from a device that is configured for MPLS:

Router#show mpls interface
Interface      IP           Tunnel  BGP Static Operational 
Ethernet0/0    Yes (ldp)    No      No  No     Yes
Router#

To determine the software running on a Cisco product, log in to the device and issue the "show version" command to display the system banner. Cisco IOS software will identify itself as "Internetwork Operating System Software" or simply "IOS". On the next line of output, the image name will be displayed between parentheses, followed by "Version" and the IOS release name. Other Cisco devices will not have the "show version" command or will give different output.

The following example identifies a Cisco product that is running Cisco IOS release 12.4(11)T2:

Router#show version 
Cisco IOS Software,7200 Software (C7200-ADVSECURITYK9-M), Version 12.4(11)T2, RELEASE SOFTWARE (fc4) 
Technical Support: http://www.cisco.com/techsupport 
Copyright (c) 1986-2007 by Cisco Systems, Inc. 
Compiled Tue 01-May-07 04:19 by prod_rel_team
 
 <output truncated>

Additional information on the Cisco IOS release naming conventions can be found on the document entitled "White Paper: Cisco IOS Reference Guide", which is available at http://www.cisco.com/warp/public/620/1.html

Products Confirmed Not Vulnerable

Devices running Cisco IOS software versions that do not include MFI are not vulnerable.

Devices that are not configured for MPLS are not vulnerable.

Devices that are running Cisco IOS XR software are not vulnerable.

No other Cisco products are currently known to be affected by these vulnerabilities.

Details

In newer versions of Cisco IOS software, a new packet forwarding infrastructure was introduced to improve scalability and performance. This forwarding infrastructure, called MFI, is transparent to the user. MFI manages MPLS data structures used for forwarding and replaces the older implementation, Label Forwarding Information Base (LFIB). Cisco IOS MFI implementation is vulnerable to a DoS attack from specially crafted packets that are handled in the software path, including transit packets that are handled in the software path. Such packets can be sent from the local segment to the interfaces that are configured for MPLS or via tunnel interfaces that are configured for MPLS. To target a remote system in an MPLS network, an attacker needs to have access to the MPLS network through an MPLS-enabled interface. MPLS packets are dropped on interfaces that are not configured for MPLS.

Devices that support MFI will have mfi_ios in the output of the show subsys command. Interfaces that are enabled for MPLS can be seen by the show mpls interface command.

More information on MFI can be found at the following link:

http://www.cisco.com/en/US/docs/ios/mpls/configuration/guide/mp_lsc_removed.html

This vulnerability is documented in the Cisco Bug ID CSCsk93241 ( registered customers only) and has been assigned Common Vulnerabilities and Exposures (CVE) ID CVE-2008-3804.

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 .

CSCsk93241 - Chunk memory corruption on LFDp Input Proc Calculate the environmental score of CSCsk93241
CVSS Base Score - 7.8
Access Vector	Access Complexity	Authentication	Confidentiality Impact	Integrity Impact	Availability Impact
Network	Low	None	None	None	Complete
CVSS Temporal Score - 6.4
Exploitability		Remediation Level		Report Confidence
Functional		Official-Fix		Confirmed

Impact

Successful exploitation of this vulnerability may result in the reload of the device, leading to a 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.

Each row of the Cisco IOS software table (below) names a Cisco IOS release train. If a given release train is vulnerable, then the earliest possible releases that contain the fix (along with the anticipated date of availability for each, if applicable) are listed in the "First Fixed Release" column of the table. The "Recommended Release" column indicates the releases which have fixes for all the published vulnerabilities at the time of this Advisory. 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. Cisco recommends upgrading to a release equal to or later than the release in the "Recommended Releases" column of the table.

Major Release	Availability of Repaired Releases
Affected 12.0-Based Releases	First Fixed Release	Recommended Release
There are no affected 12.0 based releases
Affected 12.1-Based Releases	First Fixed Release	Recommended Release
There are no affected 12.1 based releases
Affected 12.2-Based Releases	First Fixed Release	Recommended Release
12.2	Not Vulnerable
12.2B	Not Vulnerable
12.2BC	Not Vulnerable
12.2BW	Not Vulnerable
12.2BX	Not Vulnerable
12.2BY	Not Vulnerable
12.2BZ	Not Vulnerable
12.2CX	Not Vulnerable
12.2CY	Not Vulnerable
12.2CZ	Not Vulnerable
12.2DA	Not Vulnerable
12.2DD	Not Vulnerable
12.2DX	Not Vulnerable
12.2EW	Not Vulnerable
12.2EWA	Not Vulnerable
12.2EX	Not Vulnerable
12.2EY	12.2(44)EY; Available on 16-DEC-08
12.2EZ	Not Vulnerable
12.2FX	Not Vulnerable
12.2FY	Not Vulnerable
12.2FZ	Not Vulnerable
12.2IRB	Not Vulnerable
12.2IXA	Not Vulnerable
12.2IXB	Not Vulnerable
12.2IXC	Not Vulnerable
12.2IXD	Not Vulnerable
12.2IXE	Not Vulnerable
12.2IXF	Not Vulnerable
12.2IXG	Not Vulnerable
12.2JA	Not Vulnerable
12.2JK	Not Vulnerable
12.2MB	Not Vulnerable
12.2MC	Not Vulnerable
12.2S	Releases prior to 12.2(22)S are not vulnerable. Release 12.2(22)S and later and prior to 12.2(30)S are vulnerable, release 12.2(30)S and later are not vulnerable	12.2(33)SB2; Available on 26-SEP-08
12.2SB	12.2(31)SB12 12.2(33)SB	12.2(33)SB2; Available on 26-SEP-08
12.2SBC	Vulnerable; first fixed in 12.2SB	12.2(33)SB2; Available on 26-SEP-08
12.2SCA	12.2(33)SCA1	12.2(33)SCA1
12.2SE	12.2(44)SE3; Available on 30-SEP-08 12.2(46)SE	12.2(46)SE
12.2SEA	Not Vulnerable
12.2SEB	Not Vulnerable
12.2SEC	Not Vulnerable
12.2SED	Vulnerable; first fixed in 12.2SE	12.2(46)SE
12.2SEE	Vulnerable; first fixed in 12.2SE	12.2(46)SE
12.2SEF	Not Vulnerable
12.2SEG	Note: Releases prior to 12.2(25)SEG4 are vulnerable, release 12.2(25)SEG4 and later are not vulnerable;	12.2(25)SEG6
12.2SG	12.2(50)SG; Available on 24-NOV-08	12.2(46)SG1
12.2SGA	Not Vulnerable
12.2SL	Not Vulnerable
12.2SM	Not Vulnerable
12.2SO	Not Vulnerable
12.2SRA	Vulnerable; first fixed in 12.2SRB	12.2(33)SRB4 12.2(33)SRC2
12.2SRB	12.2(33)SRB4	12.2(33)SRB4
12.2SRC	12.2(33)SRC1	12.2(33)SRC2
12.2SU	Not Vulnerable
12.2SV	Vulnerable; contact TAC
12.2SVA	Vulnerable; contact TAC
12.2SVC	Vulnerable; contact TAC
12.2SVD	Vulnerable; contact TAC
12.2SW	Note: Releases prior to 12.2(25)SW4 are vulnerable, release 12.2(25)SW4 and later are not vulnerable;	12.2(25)SW12
12.2SX	Not Vulnerable
12.2SXA	Not Vulnerable
12.2SXB	Not Vulnerable
12.2SXD	Not Vulnerable
12.2SXE	Not Vulnerable
12.2SXF	Not Vulnerable
12.2SXH	12.2(33)SXH3	12.2(33)SXH3
12.2SY	Not Vulnerable
12.2SZ	Not Vulnerable
12.2T	Not Vulnerable
12.2TPC	Not Vulnerable
12.2XA	Not Vulnerable
12.2XB	Not Vulnerable
12.2XC	Not Vulnerable
12.2XD	Not Vulnerable
12.2XE	Not Vulnerable
12.2XF	Not Vulnerable
12.2XG	Not Vulnerable
12.2XH	Not Vulnerable
12.2XI	Not Vulnerable
12.2XJ	Not Vulnerable
12.2XK	Not Vulnerable
12.2XL	Not Vulnerable
12.2XM	Not Vulnerable
12.2XN	Vulnerable; first fixed in 12.2SB	12.2(33)SB2; Available on 26-SEP-08 12.2(33)SRC2 12.2(33)XNA2
12.2XNA	Not Vulnerable
12.2XNB	Not Vulnerable
12.2XO	Not Vulnerable
12.2XQ	Not Vulnerable
12.2XR	Not Vulnerable
12.2XS	Not Vulnerable
12.2XT	Not Vulnerable
12.2XU	Not Vulnerable
12.2XV	Not Vulnerable
12.2XW	Not Vulnerable
12.2YA	Not Vulnerable
12.2YB	Not Vulnerable
12.2YC	Not Vulnerable
12.2YD	Not Vulnerable
12.2YE	Not Vulnerable
12.2YF	Not Vulnerable
12.2YG	Not Vulnerable
12.2YH	Not Vulnerable
12.2YJ	Not Vulnerable
12.2YK	Not Vulnerable
12.2YL	Not Vulnerable
12.2YM	Not Vulnerable
12.2YN	Not Vulnerable
12.2YO	Not Vulnerable
12.2YP	Not Vulnerable
12.2YQ	Not Vulnerable
12.2YR	Not Vulnerable
12.2YS	Not Vulnerable
12.2YT	Not Vulnerable
12.2YU	Not Vulnerable
12.2YV	Not Vulnerable
12.2YW	Not Vulnerable
12.2YX	Not Vulnerable
12.2YY	Not Vulnerable
12.2YZ	Not Vulnerable
12.2ZA	Not Vulnerable
12.2ZB	Not Vulnerable
12.2ZC	Not Vulnerable
12.2ZD	Not Vulnerable
12.2ZE	Not Vulnerable
12.2ZF	Not Vulnerable
12.2ZG	Not Vulnerable
12.2ZH	Not Vulnerable
12.2ZJ	Not Vulnerable
12.2ZL	Not Vulnerable
12.2ZP	Not Vulnerable
12.2ZU	Not Vulnerable
12.2ZX	Vulnerable; first fixed in 12.2SB	12.2(33)SB2; Available on 26-SEP-08
12.2ZY	Not Vulnerable
12.2ZYA	Not Vulnerable
Affected 12.3-Based Releases	First Fixed Release	Recommended Release
There are no affected 12.3 based releases
Affected 12.4-Based Releases	First Fixed Release	Recommended Release
12.4	Not Vulnerable
12.4JA	Not Vulnerable
12.4JK	Not Vulnerable
12.4JL	Not Vulnerable
12.4JMA	Not Vulnerable
12.4JMB	Not Vulnerable
12.4JMC	Not Vulnerable
12.4JX	Not Vulnerable
12.4MD	Not Vulnerable
12.4MR	Not Vulnerable
12.4SW	Not Vulnerable
12.4T	Not Vulnerable
12.4XA	Not Vulnerable
12.4XB	Not Vulnerable
12.4XC	Not Vulnerable
12.4XD	Not Vulnerable
12.4XE	Not Vulnerable
12.4XF	Not Vulnerable
12.4XG	Not Vulnerable
12.4XJ	Not Vulnerable
12.4XK	Not Vulnerable
12.4XL	Not Vulnerable
12.4XM	Not Vulnerable
12.4XN	Not Vulnerable
12.4XP	Not Vulnerable
12.4XQ	12.4(15)XQ1	12.4(15)XQ1
12.4XR	Vulnerable; migrate to any release in 12.4T	12.4(15)T7
12.4XT	Not Vulnerable
12.4XV	Not Vulnerable
12.4XW	Not Vulnerable
12.4XY	12.4(15)XY4	12.4(15)XY4
12.4XZ	12.4(15)XZ1	12.4(15)XZ2
12.4YA	Not Vulnerable

Workarounds

MPLS is normally enabled on physical and logical interfaces that are shared with other MPLS-enabled devices. It can be disabled on interfaces where MPLS is not necessary and from which a potential attack can be launched. This action may help to limit the exposure of this vulnerability.

If it is not possible to disable MPLS on interfaces from which an attack can be launched, there are no workarounds to mitigate this vulnerability.

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/warp/public/687/Directory/DirTAC.shtml 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.

This vulnerability was found internally.

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://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20080924-mfi

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 1.1	2009-April-16	Removed references to the combined software table, as it is now outdated.
Revision 1.0	2008-Sep-24	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/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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Cisco Security Advisory

Cisco IOS MPLS Forwarding Infrastructure Denial of Service Vulnerability

Advisory ID: cisco-sa-20080924-mfi

Revision 1.1

For Public Release 2008 September 24 16:00 UTC (GMT)

Contents

writePM('affected')Affected Products

writePM('vps') Vulnerable Products

writePM('nonvulnerable')Products Confirmed Not Vulnerable

writePM('details')Details

writePM('vulnerability')Vulnerability Scoring Details

writePM('impact')Impact

writePM('software')Software Versions and Fixes

writePM('workarounds')Workarounds

writePM('fixes')Obtaining Fixed Software

writePM('CustomerswithServiceContracts')Customers with Service Contracts

writePM('CustomerSupportOrganizationsConcepts')Customers Using Third-Party Support Organizations

writePM('CustomerswithoutServiceContracts')Customers Without Service Contracts

writePM('exploitation')Exploitation and Public Announcements

writePM('status')Status of This Notice: Final

writePM('distribution')Distribution

writePM('revision')Revision History

writePM('secpro')Cisco Security Procedures

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