Cisco Security Advisory
Cisco IOS MPLS Forwarding Infrastructure Denial of Service Vulnerability
AV:N/AC:L/Au:N/C:N/I:N/A:C/E:F/RL:OF/RC:C
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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 software updates that address this vulnerability.
This advisory is posted at https://sec.cloudapps.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:
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https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20080924-iosips
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https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20080924-ssl
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https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20080924-sip
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https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20080924-cucm
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https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20080924-vpn
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https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20080924-ipc
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https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20080924-ubr
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https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20080924-multicast
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https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20080924-sccp
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https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20080924-iosfw
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https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20080924-l2tp
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https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20080924-iosips
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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
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.
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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.
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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.
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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
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
12.2(44)EY; Available on 16-DEC-08
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
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
12.2(31)SB12
12.2(33)SB
12.2(33)SB2; Available on 26-SEP-08
Vulnerable; first fixed in 12.2SB
12.2(33)SB2; Available on 26-SEP-08
12.2(33)SCA1
12.2(33)SCA1
12.2(44)SE3; Available on 30-SEP-08
12.2(46)SE
12.2(46)SE
Not Vulnerable
Not Vulnerable
Not Vulnerable
Vulnerable; first fixed in 12.2SE
12.2(46)SE
Vulnerable; first fixed in 12.2SE
12.2(46)SE
Not Vulnerable
Note: Releases prior to 12.2(25)SEG4 are vulnerable, release 12.2(25)SEG4 and later are not vulnerable;
12.2(25)SEG6
12.2(50)SG; Available on 24-NOV-08
12.2(46)SG1
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Vulnerable; first fixed in 12.2SRB
12.2(33)SRB4
12.2(33)SRC2
12.2(33)SRB4
12.2(33)SRB4
12.2(33)SRC1
12.2(33)SRC2
Not Vulnerable
Vulnerable; contact TAC
Vulnerable; contact TAC
Vulnerable; contact TAC
Vulnerable; contact TAC
Note: Releases prior to 12.2(25)SW4 are vulnerable, release 12.2(25)SW4 and later are not vulnerable;
12.2(25)SW12
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
12.2(33)SXH3
12.2(33)SXH3
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Vulnerable; first fixed in 12.2SB
12.2(33)SB2; Available on 26-SEP-08
12.2(33)SRC2
12.2(33)XNA2
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Vulnerable; first fixed in 12.2SB
12.2(33)SB2; Available on 26-SEP-08
Not Vulnerable
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
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
12.4(15)XQ1
12.4(15)XQ1
Vulnerable; migrate to any release in 12.4T
12.4(15)T7
Not Vulnerable
Not Vulnerable
Not Vulnerable
12.4(15)XY4
12.4(15)XY4
12.4(15)XZ1
12.4(15)XZ2
Not Vulnerable
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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.
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To learn about Cisco security vulnerability disclosure policies and publications, see the Security Vulnerability Policy. This document also contains instructions for obtaining fixed software and receiving security vulnerability information from Cisco.
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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.
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