__________________________________________________________ The U.S. Department of Energy Computer Incident Advisory Capability ___ __ __ _ ___ / | /_\ / \___ __|__ / \ \___ __________________________________________________________ INFORMATION BULLETIN Crafted Packet Causes Reload on Cisco Routers [Cisco Document ID: 63846] January 26, 2005 17:00 GMT Number P-110 [REVISED 28 Jan 2005] ______________________________________________________________________________ PROBLEM: Cisco Routers running Internetwork Operating System (IOS) that supports Multi Protocol Label Switching (MPLS) are vulnerable to a Denial of Service (DoS) attack on intergaces where MPLS is not configured. A system that supports MPLS is vulnerable even if that system is not configured for MPLS. PLATFORM: Only the following products running a vulnerable version of IOS that support MPLS are affected: * 2600 and 2800 series routers * 3600, 3700, and 2800 series routers * 4500 and 4700 series routers * 5300, 5350, and 5400 series Access Servers DAMAGE: Successful exploitation of this vulnerability could result in a reload of the device. Repeated exploitation could result in a sustained DoS attack. SOLUTION: Upgrade to the appropriate version. ______________________________________________________________________________ VULNERABILITY The risk is MEDIUM. A malformed packet may cause a device to ASSESSMENT: reload. ______________________________________________________________________________ LINKS: CIAC BULLETIN: http://www.ciac.org/ciac/bulletins/p-110.shtml ORIGINAL BULLETIN: Cisco Document ID: 63846 http://www.cisco.com/en/US/products/products_security_ advisory09186a00803be77c.shtml ______________________________________________________________________________ REVISION HISTORY: 01/28/2005 - revised to reflect the changes Cisco has made to Cisco Security Advisory: Crafted Packet Causes Reload on Cisco Routers Document ID: 63846 in the Summary section and in the Software Versions and Fixes sections. [***** Start Cisco Document ID: 63846 *****] Cisco Security Advisory: Crafted Packet Causes Reload on Cisco Routers Document ID: 63846 Revision 1.1 Last Updated 2005 January 28 1800 (GMT) For Public Release 2005 January 26 1600 (GMT) -------------------------------------------------------------------------------- -------------------------------------------------------------------------------- Contents Summary Affected Products Details Impact Software Versions and Fixes Obtaining Fixed Software Workarounds Exploitation and Public Announcements Status of This Notice: FINAL Distribution Revision History Cisco Security Procedures -------------------------------------------------------------------------------- Summary Cisco Routers running Internetwork Operating System (IOS) that supports Multi Protocol Label Switching (MPLS) are vulnerable to a Denial of Service (DoS) attack on interfaces where MPLS is not configured. A system that supports MPLS is vulnerable even if that system is not configured for MPLS. The vulnerability is only present in Cisco IOS release trains based on 12.1T, 12.2, 12.2T, 12.3 and 12.3T. Releases based on 12.1 mainline, 12.1E and all releases prior to 12.1 are not vulnerable. Cisco has made free software available to address this vulnerability. There are workarounds available to mitigate the effects. This issue is tracked by CERT/CC VU#583638. This advisory is available at http://www.cisco.com/warp/public/707/cisco-sa- 20050126-les.shtml. Affected Products Vulnerable Products Only the following products running a vulnerable version of IOS that support MPLS are affected. 2600 and 2800 series routers 3600, 3700 and 3800 series routers 4500 and 4700 series routers 5300, 5350 and 5400 series Access Servers Products that are not listed above are not affected. MPLS is not supported in IP and IP Plus feature sets. Therefore, products running an IOS version with an IP or IP Plus feature set are not vulnerable. An attack can only be launched at systems that are not configured for MPLS Traffic Engineering and on the interfaces where MPLS is not enabled. MPLS enabled interfaces can be determined by the show mpls interfaces command. An unaffacted system where MPLS is not supported will give an output similar to the following. Router#show mpls interfaces ^ % Invalid input detected at '^' marker. Router# MPLS can be enabled in different ways on a router. In the below output, a router is shown that has MPLS enabled for IP on interface Ethernet0/0. Router#show mpls interfaces Interface IP Tunnel Operational Ethernet0/0 Yes (tdp) No Yes Router# When MPLS for IP is enabled on an interface, the router is immune to the attacks coming from that interface but vulnerable to the attacks coming from other interfaces. Enabling MPLS for IP on all interfaces of the router will make the router immune to attacks coming from any interface. An interface that has MPLS for IP enabled will have mpls ip or tag-switching ip command in the interface configuration. MPLS Traffic Engineering (TE) provides a better protection against this vulnerability. If MPLS TE is enabled globally, the router will be immune to the attacks coming from any interface. A router that has MPLS TE enabled will have mpls traffic-eng tunnels command in the show running-config output. Products Confirmed Not Vulnerable Products that are not running Cisco IOS are not vulnerable. Products running Cisco IOS versions 12.0 and earlier and 12.1 mainline are not vulnerable. Products that are not mentioned in the Affected Products section are not vulnerable (including but not limited to Cisco 7200, 7500, 12000 series and Catalyst systems). No other Cisco products are currently known to be affected by these vulnerabilities. Details Multi Protocol Label Switching (MPLS) is a vendor-independent protocol that integrates layer-2 (as defined in the Open System Interconnection Reference Model) information into layer-3. More information on MPLS can be found at http://www.cisco. com/warp/public/732/Tech/mpls. A vulnerability exists in the processing of an MPLS packet that is received on an interface where MPLS is disabled. A router that is configured for MPLS Traffic Engineering is immune to attacks coming from any interface. A Cisco device receiving a crafted packet on an MPLS disabled interface will reset and may take several minutes to become fully functional. This vulnerability may be exploited repeatedly resulting in an extended DoS attack. This issue is documented in bugs ID CSCeb56909 ( registered customers only) and CSCec86420 ( registered customers only) . Such crafted packets can only be sent from the local network segment. Impact Successful exploitation of this vulnerability could result in a reload of the device. Repeated exploitation could result in a sustained DoS attack. Software Versions and Fixes Major Release Availability of Repaired Releases Affected 12.1-Based Release Rebuild Maintenance 12.1DB Migrate to 12.3(4)T or later 12.1DC Migrate to 12.3(4)T or later 12.1T Migrate to 12.2 or later 12.1XG Migrate to 12.3 or later 12.1XI Migrate to 12.2 or later 12.1XJ Migrate to 12.3 or later 12.1XL Migrate to 12.3 or later 12.1XM Migrate to 12.3 or later 12.1XP Migrate to 12.3 or later 12.1XQ Migrate to 12.3 or later 12.1XR Migrate to 12.3 or later 12.1XT Migrate to 12.3 or later 12.1XU Migrate to 12.3 or later 12.1XV Migrate to 12.3 or later 12.1YA Migrate to 12.3 or later 12.1YB Migrate to 12.3 or later 12.1YC Migrate to 12.3 or later 12.1YD Migrate to 12.3 or later 12.1YE Migrate to 12.3 or later 12.1YF Migrate to 12.3 or later 12.1YH Migrate to 12.3 or later 12.1YI Migrate to 12.3 or later Affected 12.2-Based Release Rebuild Maintenance 12.2 12.2(10g) 12.2(13e) 12.2(16f) 12.2(17d) 12.2(19b) 12.2(21a) 12.2(23) 12.2B 12.2(2)B through 12.2(4)B7, Migrate to 12.3 or later 12.2(4)B8 and forward, Migrate to 12.3(4)T or later 12.2BC 12.2(15)BC2 12.2BW Migrate to 12.3 or later 12.2BX Migrate to 12.3(7)XI1 or later 12.BY Migrate to 12.3(4)T or later 12.2BZ Migrate to 12.3(7)XI1 or later 12.2CX Migrate to 12.2(15)BC2 12.2CY Migrate to 12.2(15)BC2 12.2CZ 12.2(15)CZ 12.2DA 12.2(12)DA6 12.2DD Migrate to 12.3(4)T or later 12.2DX Migrate to 12.3(4)T or later 12.2EW 12.2(18)EW 12.2EWA 12.2(20)EWA 12.2JA 12.2(15)JA 12.2JK 12.2(15)JK 12.2MB Migrate to 12.2(19)SW 12.2MC Migrate to 12.3(11)T 12.2MX Migrate to 12.3(8)T or later 12.2SU 12.2(14)SU 12.2SW 12.2(19)SW 12.2SY Migrate to 12.2(17d)SXB or later 12.2SZ Migrate to 12.2(20)S4 12.2T 12.2(13)T14 12.2(15)T7 12.2XA Migrate to 12.3 or later 12.2XB 12.2(2)XB18 12.2XC Migrate to 12.3T or later 12.2XD Migrate to 12.3 or later 12.2XE Migrate to 12.3 or later 12.2XF Migrate to 12.2(15)BC2 12.2XG Migrate to 12.3 or later 12.2XH Migrate to 12.3 or later 12.2XI Migrate to 12.3 or later 12.2XJ Migrate to 12.3 or later 12.2XK Migrate to 12.3 or later 12.2XL Migrate to 12.3 or later 12.2XM Migrate to 12.3 or later 12.2XN Migrate to 12.3 or later 12.2XQ Migrate to 12.3 or later 12.2XR 12.2(15)XR 12.2XS Migrate to 12.3 or later 12.2XT Migrate to 12.3 or later 12.2XU Migrate to 12.3 or later 12.2XV No plan. 12.2XW Migrate to 12.3 or later 12.2XZ Migrate to 12.3 or later 12.2YA 12.2(4)YA8 12.2YB Migrate to 12.3 or later 12.2YC Migrate to 12.3 or later 12.2YD Migrate to 12.3(8)T or later 12.2YE Migrate to 12.2(18)S or later 12.2YF Migrate to 12.3 or later 12.2YG Migrate to 12.3 or later 12.2YH Migrate to 12.3 or later 12.2YJ Migrate to 12.3 or later 12.2YL Migrate to 12.3T or later 12.2YM Migrate to 12.3T or later 12.2YN Migrate to 12.3T or later 12.2YO Migrate to 12.2(17d)SXB or later 12.2YQ Migrate to 12.3(4)T or later 12.2YR Migrate to 12.3(4)T or later 12.2YS Migrate to 12.3T or later 12.2YU Migrate to 12.3(2)T or later 12.2YV Migrate to 12.3(4)T or later 12.2YW Migrate to 12.3(2)T or later 12.2YX Migrate to 12.2(14)SU 12.2YZ Migrate to 12.2(20)S4 12.2ZB Migrate to 12.3T or later 12.2ZC Migrate to 12.3T or later 12.2ZD Migrate to 12.3 or later 12.2ZE Migrate to 12.3 or later 12.2ZF Migrate to 12.3(4)T or later 12.2ZG Migrate to 12.3(4)T or later 12.2ZH Migrate to 12.3(4)T or later 12.2ZI Migrate to 12.2(18)S or later 12.2ZJ Migrate to 12.3T or later 12.2ZL Migrate to 12.3(7)T or later 12.2ZN Migrate to 12.3T or later 12.2ZO Migrate to 12.3 or later 12.2ZP No plan. Affected 12.3-Based Release Rebuild Maintenance 12.3 12.3(3f) 12.3(5) 12.3B 12.3(5a)B4 12.3BC 12.3(9a)BC 12.3BW Migrate to 12.3(5a)B or later 12.3T 12.3(2)T5 12.3(4)T7 12.3(7)T 12.3XA Migrate to 12.3(7)T or later 12.3XB Migrate to 12.3(8)T or later 12.3XC Migrate to 12.3(2)XC3 - Availablility date TBD 12.3XD 12.3(4)XD 12.3XE 12.3(2)XE1 12.3XF 12.3(2)XF 12.3XG 12.3(4)XG1 12.3XH 12.3(4)XH 12.3XI 12.3(7)XI 12.3XJ 12.3(7)XJ 12.3XK 12.3(4)XK1 12.3XL 12.3(7)XL 12.3XM 12.3(7)XM 12.3XN 12.3(4)XN 12.3XQ 12.3(4)XQ 12.3XR 12.3(7)XR 12.3XS 12.3(7)XS 12.3XT 12.3(2)XT 12.3XU 12.3(8)XU 12.3XW 12.3(8)XW 12.3XX 12.3(8)XX 12.3XY 12.3(8)XY 12.3YA 12.3(8)YA 12.3YD 12.3(8)YD 12.3YE 12.3(4)YE 12.3YF 12.3(11)YF 12.3YG 12.3(8)YG 12.3YH 12.3(8)YH When considering software upgrades, please also consult http://www.cisco.com /en/US/products/products_security_advisories_listing.html 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) for assistance. Obtaining Fixed Software 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 assistance with the upgrade, which should be free of charge. 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 Please 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 TAC. Please do not contact either "psirt@cisco.com" or "security-alert@cisco.com" for software upgrades. See 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. 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 http://www.cisco.com/public/sw-center/sw-usingswc. shtml. Workarounds The effectiveness of any workaround 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 is the most appropriate for use in the intended network before it is deployed. Warning: Using this workaround may affect the operation of your network and might cause problems. Therefore it is strongly recommended that you do a code upgrade if you are affected. It is not recommended that you use the workaround as a long term solution. Enabling MPLS Traffic Engineering (MPLS TE) globally can be used as a workaround to mitigate this vulnerability. Since MPLS requires Cisco Express Forwarding (CEF) in order to work, CEF needs to be enabled first in order to enable MPLS TE. CEF and MPLS TE can be enabled by the following commands. Router(config)# ip cef Router(config)# mpls traffic-eng tunnels Having MPLS TE enabled will make the router immune to the attacks coming from any interface. 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 Notice: FINAL THIS ADVISORY IS PROVIDED ON AN "AS IS" BASIS AND DOES NOT IMPLY ANY KIND OF GUARANTEE OR WARRANTY, INCLUDING THE WARRANTY OF MERCHANTABILITY. YOUR USE OF THE INFORMATION ON THE ADVISORY OR MATERIALS LINKED FROM THE ADVISORY IS AT YOUR OWN RISK. CISCO RESERVES THE RIGHT TO CHANGE OR UPDATE THIS NOTICE AT ANY TIME. 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/cisco-sa-20050126-les.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 and Usenet news recipients. cust-security-announce@cisco.com first-teams@first.org (includes CERT/CC) bugtraq@securityfocus.com vulnwatch@vulnwatch.org cisco@spot.colorado.edu cisco-nsp@puck.nether.net full-disclosure@lists.netsys.com comp.dcom.sys.cisco@newsgate.cisco.com Various internal Cisco mailing lists 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 1.0 2005-January-26 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. [***** End Cisco Document ID: 63846 *****] _______________________________________________________________________________ CIAC wishes to acknowledge the contributions of Cisco Systems for the information contained in this bulletin. _______________________________________________________________________________ CIAC, the Computer Incident Advisory Capability, is the computer security incident response team for the U.S. Department of Energy (DOE) and the emergency backup response team for the National Institutes of Health (NIH). CIAC is located at the Lawrence Livermore National Laboratory in Livermore, California. CIAC is also a founding member of FIRST, the Forum of Incident Response and Security Teams, a global organization established to foster cooperation and coordination among computer security teams worldwide. CIAC services are available to DOE, DOE contractors, and the NIH. 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Neither the United States Government nor the University of California nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial products, process, or service by trade name, trademark, manufacturer, or otherwise, does not necessarily constitute or imply its endorsement, recommendation or favoring by the United States Government or the University of California. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or the University of California, and shall not be used for advertising or product endorsement purposes. 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