__________________________________________________________ The U.S. Department of Energy Computer Incident Advisory Capability ___ __ __ _ ___ / | /_\ / \___ __|__ / \ \___ __________________________________________________________ INFORMATION BULLETIN Crafted TCP Packet Can Cause Denial of Service [Cisco Security Advisory Document ID: 72318] January 25, 2007 14:00 GMT Number R-112 [REVISED 1 Feb 2007] ______________________________________________________________________________ PROBLEM: The Cisco IOS Transmission Control Protocol (TCP) listener in certain versions of Cisco IOS software is vulnerable to a remotely-exploitable memory leak that may lead to a denial of service condition. PLATFORM: All unfixed versions of Cisco IOS software, 9.x, 10.x, 11.x, and 12.x DAMAGE: A memory leak that may lead to a denial of service condition. SOLUTION: Upgrade to the appropriate version. ______________________________________________________________________________ VULNERABILITY The risk is MEDIUM. Vulnerable to a remotely-exploitable memory ASSESSMENT: leak that may lead to a denial of service condition. ______________________________________________________________________________ LINKS: CIAC BULLETIN: http://www.ciac.org/ciac/bulletins/r-112.shtml ORIGINAL BULLETIN: Cisco Security Advisory Document ID: 72318 http://www.cisco.com/en/US/products/products_security_ advisory09186a00807cb0e4.shtml ______________________________________________________________________________ REVISION HISTORY: 02/01/2007 - revised to reflect changes Cisco has made to Document ID: 72318 where they updated BGP and MD5. [***** Start Cisco Security Advisory Document ID: 72318 *****] Cisco Security Advisory: Crafted TCP Packet Can Cause Denial of Service Document ID: 72318 Advisory ID: cisco-sa-20070124-crafted-tcp http://www.cisco.com/warp/public/707/cisco-sa-20070124-crafted-tcp.shtml 1.1 Last Updated 2007 January 31 0130 UTC For Public Release 2007 January 24 1600 UTC (GMT) -------------------------------------------------------------------------------- -------------------------------------------------------------------------------- Contents Summary Affected Products Details Vulnerability Scoring Details Impact Software Version and Fixes Workarounds Obtaining Fixed Software Exploitation and Public Announcements Status of this Notice:FINAL Distribution Revision History Cisco Security Procedures -------------------------------------------------------------------------------- Summary The Cisco IOS Transmission Control Protocol (TCP) listener in certain versions of Cisco IOS software is vulnerable to a remotely-exploitable memory leak that may lead to a denial of service condition. This vulnerability only applies to traffic destined to the Cisco IOS device. Traffic transiting the Cisco IOS device will not trigger this vulnerability. Cisco has made free software available to address this vulnerability for affected customers. This issue is documented as Cisco bug ID CSCek37177 ( registered customers only) . There are workarounds available to mitigate the effects of the vulnerability. This advisory is posted at http://www.cisco.com/warp/public/707/cisco-sa-20070124-crafted-tcp.shtml. Affected Products Vulnerable Products This issue affects all Cisco devices running Cisco IOS software. To be affected, devices must be configured to process Internet Protocol version 4 (IPv4) packets and receive TCP packets. Devices which run only Internet Protocol version 6 (IPv6) are not affected. This vulnerability is present in all unfixed versions of Cisco IOS software, including versions 9.x, 10.x, 11.x and 12.x. 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 running Cisco IOS release 12.2(14)S16 with an installed image name of C7200-IS-M: Cisco Internetwork Operating System Software IOS (tm) 7200 Software (C7200-IS-M), Version 12.2(14)S16, RELEASE SOFTWARE (fc1)The release train label is "12.2". The next example shows a product running IOS release 12.3(7)T12 with an image name of C7200-IK9S-M: Cisco IOS Software, 7200 Software (C7200-IK9S-M), Version 12.3(7)T12, RELEASE SOFTWARE (fc1) Additional information about Cisco IOS Banners is available at: http://www.cisco.com/en/US/products/sw/iosswrel/ps1828/products_white_paper09186a008018305e.shtml#3 Products Confirmed Not Vulnerable Cisco products that do not run IOS are unaffected by this vulnerability. Cisco IOS-XR is not affected. No other Cisco products are currently known to be affected by this vulnerability. Details TCP is the transport layer protocol designed to provide connection-oriented, reliable delivery of a data stream. To accomplish this, TCP uses a mixture of flags to indicate state and sequence numbers to identify the order in which the packets are to be reassembled. TCP also provides a number, called an acknowledgement number, that is used to indicate the sequence number of the next packet expected. The full specification of the TCP protocol can be found at http://www.ietf.org/rfc/rfc0793.txt . Cisco IOS devices that are configured to receive TCP packets are exposed to this issue. This Advisory does not apply to traffic that is transiting the device. Certain crafted packets destined to an IPv4 address assigned to a physical or virtual interface on a Cisco IOS device may cause the device to leak a small amount of memory. Over time, such a memory leak may lead to memory exhaustion and potentially degraded service. Although this is an issue with TCP, it is not required to complete the TCP 3-way handshake in order for the memory leak to be triggered. Therefore, TCP packets with a spoofed source address may trigger the leak. The following document contains additional information on how to identify if your router is suffering from a memory leak in Processor memory: http://www.cisco.com/en/US/products/sw/iosswrel/ps1831/products_tech_note09186a00800a6f3a.shtml#tshoot2 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: 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: http://intellishield.cisco.com/security/alertmanager/cvss CSCek37177 - malformed tcp packets deplete processor memory ( registered customers only) Calculate the environmental score of CSCek37177 CVSS Base Score - 3.3 Access Vector Access Complexity Authentication Confidentiality Impact Integrity Impact Availability Impact Impact Bias Remote Low Not Required None None Complete Normal CVSS Temporal Score - 2.7 Exploitability Remediation Level Report Confidence Functional Official Fix Confirmed Impact Successful exploitation of the vulnerability may result in a small amount of processor memory to leak, which may lead to degraded service. This issue will not resolve over time, and will require a device reset to recover the leaked memory. This vulnerability only applies to traffic destined to the Cisco IOS device. Traffic transiting the device will not trigger this issue. 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 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: http://www.cisco.com/warp/public/620/1.html. Note: There are three IOS security advisories and one field notice being published on January 24, 2007. Each advisory lists only the releases which fix the issue described in the advisory. A combined software table is available at http://www.cisco.com/warp/public/707/cisco-sa-20070124-bundle.shtml and can be used to choose a software release which fixes all security vulnerabilities published as of January 24, 2007. Links for the advisories and field notice are listed here. http://www.cisco.com/warp/public/707/cisco-sa-20070124-IOS-IPv6.shtml http://www.cisco.com/warp/public/707/cisco-sa-20070124-crafted-tcp.shtml http://www.cisco.com/warp/public/707/cisco-sa-20070124-crafted-ip-option.shtml http://www.cisco.com/warp/public/770/fn62613.shtml Requests for software rebuilds to include the change for Daylight Savings Time (DST) that will be implemented in March 2007 should be directed through the Technical Assistance Center (TAC), and this advisory should be used as reference. Major Release Availability of Repaired Releases Affected 12.0-Based Release Rebuild Maintenance 12.0 Vulnerable; migrate to 12.2(37) or later 12.0DA Vulnerable; migrate to 12.2(10)DA5 or later 12.0DB Vulnerable; migrate to 12.3(4)T13 or later 12.0DC Vulnerable; migrate to 12.3(4)T13 or later 12.0S 12.0(31)S6 12.0(32)S4 12.0SC Vulnerable; migrate to 12.3(13a)BC6 or later 12.0SL Vulnerable; migrate to 12.0(31)S6 or later 12.0SP Vulnerable; migrate to 12.0(31)S6 or later 12.0ST Vulnerable; migrate to 12.0(31)S6 or later 12.0SX 12.0(25)SX11 12.0SY 12.0(32)SY 12.0SZ Vulnerable; migrate to 12.0(31)S6 or later 12.0T Vulnerable; migrate to 12.2(37) or later 12.0W Not vulnerable 12.0WC 12.0(5)WC15 12.0WT Not vulnerable 12.0XA Vulnerable; migrate to 12.2(37) or later 12.0XB Vulnerable; migrate to 12.2(37) or later 12.0XC Vulnerable; migrate to 12.2(37) or later 12.0XD Vulnerable; migrate to 12.2(37) or later 12.0XE Vulnerable; migrate to 12.1(26)E7 or later 12.0XF Not vulnerable 12.0XG Vulnerable; migrate to 12.2(37) or later 12.0XH Vulnerable; migrate to 12.2(37) or later 12.0XI Vulnerable; migrate to 12.2(37) or later 12.0XJ Vulnerable; migrate to 12.2(37) or later 12.0XK Vulnerable; migrate to 12.2(37) or later 12.0XL Vulnerable; migrate to 12.2(37) or later 12.0XM Vulnerable; migrate to 12.2(37) or later 12.0XN Vulnerable; migrate to 12.2(37) or later 12.0XQ Vulnerable; migrate to 12.2(37) or later 12.0XR Vulnerable; migrate to 12.2(37) or later 12.0XS Vulnerable; migrate to 12.1(26)E7 or later 12.0XV Vulnerable; migrate to 12.2(37) or later 12.0XW Not vulnerable Affected 12.1-Based Release Rebuild Maintenance 12.1 Vulnerable; migrate to 12.2(37) or later 12.1 AA Vulnerable; migrate to 12.2(37) or later 12.1 AX Vulnerable; migrate to 12.2(25)EY4 or later 12.1 AY Vulnerable; migrate to 12.1(22)EA8 or later 12.1 AZ Vulnerable; migrate to 12.1(22)EA8 or later 12.1 CX Vulnerable; migrate to 12.2(37) or later 12.1 DA Vulnerable; migrate to 12.2(10)DA5 or later 12.1 DB Vulnerable; migrate to 12.3(4)T13 or later 12.1 DC Vulnerable; migrate to 12.3(4)T13 or later 12.1E 12.1(26)E7 12.1(27b)E1 12.1EA 12.1(22)EA8 12.1EB Vulnerable; contact TAC 12.1EC Vulnerable; migrate to 12.3(13a)BC6 or later 12.1EO 12.1(19)EO6; available on 31-Jan-07 12.1(20)EO3 12.1EU Vulnerable; migrate to 12.2(25)EWA6 or later 12.1EV Vulnerable; migrate to 12.2(27)SV4 or later 12.1EW Vulnerable; migrate to 12.2(25)EWA6 or later 12.1EX Vulnerable; migrate to 12.1(26)E7 or later 12.1EY Vulnerable; migrate to 12.1(26)E7 or later 12.1EZ Vulnerable; migrate to 12.1(26)E7 or later 12.1T Vulnerable; migrate to 12.2(37) or later 12.1XA Vulnerable; migrate to 12.2(37) or later 12.1XB Vulnerable; migrate to 12.2(37) or later 12.1XC Vulnerable; migrate to 12.2(37) or later 12.1XD Vulnerable; migrate to 12.2(37) or later 12.1XE Vulnerable; migrate to 12.1(26)E7 or later 12.1XF Vulnerable; migrate to 12.3(19) or later 12.1XG Vulnerable; migrate to 12.3(19) or later 12.1XH Vulnerable; migrate to 12.2(37) or later 12.1XI Vulnerable; migrate to 12.2(37) or later 12.1XJ Vulnerable; migrate to 12.3(19) or later 12.1XL Vulnerable; migrate to 12.3(19) or later 12.1XM Vulnerable; migrate to 12.3(19) or later 12.1XP Vulnerable; migrate to 12.3(19) or later 12.1XQ Vulnerable; migrate to 12.3(19) or later 12.1XR Vulnerable; migrate to 12.3(19) or later 12.1XS Vulnerable; migrate to 12.2(37) or later 12.1XT Vulnerable; migrate to 12.3(19) or later 12.1XU Vulnerable; migrate to 12.3(19) or later 12.1XV Vulnerable; migrate to 12.3(19) or later 12.1XW Vulnerable; migrate to 12.2(37) or later 12.1XX Vulnerable; migrate to 12.2(37) or later 12.1XY Vulnerable; migrate to 12.2(37) or later 12.1XZ Vulnerable; migrate to 12.2(37) or later 12.1YA Vulnerable; migrate to 12.3(19) or later 12.1YB Vulnerable; migrate to 12.3(19) or later 12.1YC Vulnerable; migrate to 12.3(19) or later 12.1YD Vulnerable; migrate to 12.3(19) or later 12.1YE Vulnerable; migrate to 12.3(19) or later 12.1YF Vulnerable; migrate to 12.3(19) or later 12.1YH Vulnerable; migrate to 12.3(19) or later 12.1YI Vulnerable; migrate to 12.3(19) or later 12.1YJ Vulnerable; migrate to 12.1(22)EA8 or later Affected 12.2-Based Release Rebuild Maintenance 12.2 12.2(37) 12.2B Vulnerable; migrate to 12.3(4)T13 or later 12.2BC Vulnerable; migrate to 12.3(13a)BC6 or later 12.2BW Vulnerable; migrate to 12.3(19) or later 12.2BY Vulnerable; migrate to 12.3(4)T13 or later 12.2BZ Vulnerable; migrate to 12.3(7)XI8 or later 12.2CX Vulnerable; migrate to 12.3(13a)BC6 or later 12.2CY Vulnerable; migrate to 12.3(13a)BC6 or later 12.2CZ Vulnerable; contact TAC 12.2DA 12.2(10)DA5 12.2(12)DA10 12.2DD Vulnerable; migrate to 12.3(4)T13 or later 12.2DX Vulnerable; migrate to 12.3(4)T13 or later 12.2EU Vulnerable; migrate to 12.2(25)EWA6 or later 12.2EW Vulnerable; migrate to 12.2(25)EWA6 or later 12.2EWA 12.2(25)EWA6 12.2EX 12.2(25)EX1 12.2EY 12.2(25)EY4 12.2EZ Vulnerable; migrate to 12.2(25)SEE1 or later 12.2FX Vulnerable; migrate to 12.2(25)SEE1 or later 12.2FY Vulnerable; migrate to 12.2(25)SEE1 or later 12.2FZ All 12.2FZ releases are fixed 12.2IXA Vulnerable; migrate to 12.2(18)IXD; available 30-April-07 12.2IXB Vulnerable; migrate to 12.2(18)IXD; available 30-April-07 12.2IXC Vulnerable; migrate to 12.2(18)IXD; available 30-April-07 12.2JA Vulnerable; migrate to 12.3(8)JA2 or later 12.2JK Vulnerable; migrate to 12.4(4)T4 or later 12.2MB Vulnerable; migrate to 12.2(25)SW8 or later 12.2MC Vulnerable; migrate to 12.3(11)T11 or later 12.2S 12.2(25)S12; Available 12-Feb-07 12.2SB 12.2(28)SB2 12.2(31)SB 12.2SBC 12.2(27)SBC5 12.2SE 12.2(35)SE 12.2SEA Vulnerable; migrate to 12.2(25)SEE1 or later 12.2SEB Vulnerable; migrate to 12.2(25)SEE1 or later 12.2SEC Vulnerable; migrate to 12.2(25)SEE1 or later 12.2SED Vulnerable; migrate to 12.2(25)SEE1 or later 12.2SEE 12.2(25)SEE1 12.2SEF 12.2(25)SEF1 12.2SEG All 12.2SEG releases are fixed 12.2SG 12.2(37)SG; Available 25-Apr-07 12.2SGA All 12.2SGA releases are fixed 12.2SO 12.2(18)SO7 12.2SRA All 12.2SRA releases are fixed 12.2SRB All 12.2SRB releases are fixed 12.2SU Vulnerable; migrate to 12.4(8) or later 12.2SV 12.2(27)SV4 12.2(28)SV1 12.2(29)SV1 12.2SW 12.2(25)SW8 12.2SX Vulnerable; migrate to 12.2(18)SXD7a or later 12.2SXA Vulnerable; migrate to 12.2(18)SXD7a or later 12.2SXB Vulnerable; migrate to 12.2(18)SXD7a or later 12.2SXD 12.2(18)SXD7a 12.2SXE 12.2(18)SXE6 12.2SXF 12.2(18)SXF5 12.2SY Vulnerable; migrate to 12.2(18)SXD7a or later 12.2SZ Vulnerable; migrate to 12.2(25)S12 or later; Available 12-Feb-07 12.2T Vulnerable; migrate to 12.3(19) or later 12.2TPC Vulnerable; contact TAC 12.2XA Vulnerable; migrate to 12.3(19) or later 12.2XB Vulnerable; migrate to 12.3(19) or later 12.2XC Vulnerable; migrate to 12.3(4)T13 or later 12.2XD Vulnerable; migrate to 12.3(19) or later 12.2XE Vulnerable; migrate to 12.3(19) or later 12.2XF Vulnerable; migrate to 12.3(13a)BC6 or later 12.2XG Vulnerable; migrate to 12.3(19) or later 12.2XH Vulnerable; migrate to 12.3(19) or later 12.2XI Vulnerable; migrate to 12.3(19) or later 12.2XJ Vulnerable; migrate to 12.3(19) or later 12.2XK Vulnerable; migrate to 12.3(19) or later 12.2XL Vulnerable; migrate to 12.3(19) or later 12.2XM Vulnerable; migrate to 12.3(19) or later 12.2XN Vulnerable; migrate to 12.3(19) or later 12.2XQ Vulnerable; migrate to 12.3(19) or later 12.2XR Vulnerable; migrate to 12.3(19) or later 12.2XS Vulnerable; migrate to 12.3(19) or later 12.2XT Vulnerable; migrate to 12.3(19) or later 12.2XU Vulnerable; migrate to 12.3(19) or later 12.2XV Vulnerable; migrate to 12.3(19) or later 12.2XW Vulnerable; migrate to 12.3(19) or later 12.2YA Vulnerable; migrate to 12.3(19) or later 12.2YB Vulnerable; migrate to 12.3(19) or later 12.2YC Vulnerable; migrate to 12.3(19) or later 12.2YD Vulnerable; migrate to 12.3(11)T11 or later 12.2YE Vulnerable; migrate to 12.2(25)S12 or later; Available 12-Feb-07 12.2YF Vulnerable; migrate to 12.3(19) or later 12.2YG Vulnerable; migrate to 12.3(19) or later 12.2YH Vulnerable; migrate to 12.3(19) or later 12.2YJ Vulnerable; migrate to 12.3(19) or later 12.2YK Vulnerable; migrate to 12.3(4)T13 or later 12.2YL Vulnerable; migrate to 12.3(4)T13 or later 12.2YM Vulnerable; migrate to 12.3(4)T13 or later 12.2YN Vulnerable; migrate to 12.3(4)T13 or later 12.2YO Not vulnerable 12.2YP Vulnerable; migrate to 12.3(19) or later 12.2YQ Vulnerable; migrate to 12.3(4)T13 or later 12.2YR Vulnerable; migrate to 12.3(4)T13 or later 12.2YS Vulnerable; migrate to 12.3(4)T13 or later 12.2YT Vulnerable; migrate to 12.3(19) or later 12.2YU Vulnerable; migrate to 12.3(4)T13 or later 12.2YV Vulnerable; migrate to 12.3(4)T13 or later 12.2YW Vulnerable; migrate to 12.3(4)T13 or later 12.2YX Vulnerable; migrate to 12.4(8) or later 12.2YY Vulnerable; migrate to 12.3(4)T13 or later 12.2YZ Vulnerable; migrate to 12.2(25)S12 or later; Available 12-Feb-07 12.2ZA Vulnerable; migrate to 12.2(18)SXD7a or later 12.2ZB Vulnerable; migrate to 12.3(4)T13 or later 12.2ZC Vulnerable; migrate to 12.3(4)T13 or later 12.2ZD Vulnerable; contact TAC 12.2ZE Vulnerable; migrate to 12.3(19) or later 12.2ZF Vulnerable; migrate to 12.3(4)T13 or later 12.2ZG Vulnerable; contact TAC 12.2ZH Vulnerable; contact TAC 12.2ZJ Vulnerable; migrate to 12.3(4)T13 or later 12.2ZL Vulnerable; contact TAC 12.2ZN Vulnerable; migrate to 12.3(4)T13 or later 12.2ZP Vulnerable; migrate to 12.4(8) or later Affected 12.3-Based Release Rebuild Maintenance 12.3 12.3(10f) 12.3(19) 12.3B Vulnerable; migrate to 12.3(11)T11 or later 12.3BC 12.3(13a)BC6 12.3(17a)BC2 12.3BW Vulnerable; migrate to 13.3(11)T11 or later 12.3JA 12.3(8)JA2 12.3JEA All 12.3JEA releases are fixed 12.3JEB All 12.3JEB releases are fixed 12.3JK 12.3(2)JK2 12.3JX 12.3(7)JX4 12.3(11)JX 12.3T 12.3(4)T13 12.3(11)T11 Limited platform support is available: Contact TAC Please migrate to 12.4(8) or later 12.3TPC Vulnerable; contact TAC 12.3XA Vulnerable; contact TAC 12.3XB Vulnerable; migrate to 12.3(11)T11 or later 12.3XC Vulnerable; contact TAC 12.3XD Vulnerable; migrate to 12.3(11)T11 or later 12.3XE Vulnerable; contact TAC 12.3XF Vulnerable; migrate to 12.3(11)T11 or later 12.3XG Vulnerable; contact TAC 12.3XH Vulnerable; migrate to 12.3(11)T11 or later 12.3XI 12.3(7)XI8 12.3XJ Vulnerable; migrate to 12.3(14)YX2 or later 12.3XK Vulnerable; migrate to 12.4(8) or later 12.3XQ Vulnerable; migrate to 12.4(8) or later 12.3XR Vulnerable; contact TAC 12.3XS Vulnerable; migrate to 12.4(8) or later 12.3XU Vulnerable; migrate to 12.4(2)T5 or later 12.3XW Vulnerable; migrate to 12.3(14)YX2 or later 12.3XX Vulnerable; migrate to 12.4(8) or later 12.3XY Vulnerable; migrate to 12.4(8) or later 12.3YA Vulnerable; contact TAC 12.3YD Vulnerable; migrate to 12.4(2)T5 or later 12.3YF Vulnerable; migrate to 12.3(14)YX2 or later 12.3YG Vulnerable; migrate to 12.4(2)T5 or later 12.3YH Vulnerable; migrate to 12.4(2)T5 or later 12.3YI Vulnerable; migrate to 12.4(2)T5 or later 12.3YJ Vulnerable; migrate to 12.3(14)YQ8 or later 12.3YK Vulnerable; migrate to 12.4(4)T4 or later 12.3YM 12.3(14)YM8 12.3YQ 12.3(14)YQ8 12.3YS Vulnerable; migrate to 12.4(4)T4 or later 12.3YT Vulnerable; migrate to 12.4(4)T4 or later 12.3YU Vulnerable; contact TAC 12.3YX 12.3(14)YX2 12.3YZ 12.3(11)YZ1 Affected 12.4-Based Release Rebuild Maintenance 12.4 12.4(3e) 12.4(7b) 12.4(8) 12.4MR 12.4(6)MR1 12.4SW All 12.4SW releases are fixed 12.4T 12.4(2)T5 12.4(4)T4 12.4(6)T3 12.4(9)T 12.4XA Vulnerable; migrate to 12.4(6)T3 12.4XB Vulnerable; contact TAC 12.4XC 12.4(4)XC3 12.4XD 12.4(4)XD4 12.4XE All 12.4XE releases are fixed 12.4XG All 12.4XG releases are fixed 12.4XJ All 12.4XJ releases are fixed 12.4XP All 12.4XP releases are fixed 12.4XT All 12.4XT releases are fixed Workarounds Additional mitigations that can be deployed on Cisco devices within the network are available in the Cisco Applied Intelligence companion document for this advisory: http://www.cisco.com/warp/public/707/cisco-air-20070124-crafted-tcp.shtml Note: Configuring VTY access-class filters is not an effective mitigation strategy for this vulnerability. Infrastructure ACLs (iACL) Although it is often difficult to block traffic transiting your network, it is possible to identify traffic which should never be allowed to target your infrastructure devices and block that traffic at the border of your network. Infrastructure ACLs are considered a network security best practice and should be considered as a long-term addition to good network security as well as a workaround for this specific vulnerability. The ACL example shown below should be included as part of the deployed infrastructure access-list which will protect all devices with IP addresses in the infrastructure IP address range. A sample access list for devices running Cisco IOS is below: !--- Permit TCP services from trust hosts destined !--- to infrastructure addresses. access-list 150 permit tcp TRUSTED_HOSTS MASK INFRASTRUCTURE_ADDRESSES MASK !--- Deny TCP packets from all other sources destined to infrastructure addresses. access-list 150 deny tcp any INFRASTRUCTURE_ADDRESSES MASK !--- Permit all other traffic to transit the device. access-list 150 permit IP any any interface serial 2/0 ip access-group 150 inThe white paper entitled "Protecting Your Core: Infrastructure Protection Access Control Lists" presents guidelines and recommended deployment techniques for infrastructure protection access lists. This white paper can be obtained here: http://www.cisco.com/warp/public/707/iacl.html Receive ACLs (rACL) For distributed platforms, Receive ACLs may be an option starting in Cisco IOS Software Versions 12.0(21)S2 for the 12000 (GSR), 12.0(24)S for the 7500, and 12.0(31)S for the 10720. The Receive ACL protects the device from harmful traffic before the traffic can impact the route processor. Receive ACLs are designed to only protect the device on which it is configured. On the 12000, transit traffic is never affected by a receive ACL. Because of this, the destination IP address "any" used in the example ACL entries below only refer to the router's own physical or virtual IP addresses. On the 7500 and 10720, transit traffic with IP options set will be subject to the Receive ACL and permitted or denied accordingly. Receive ACLs are considered a network security best practice, and should be considered as a long-term addition to good network security, as well as a workaround for this specific vulnerability. The white paper entitled "GSR: Receive Access Control Lists" will help you identify and allow legitimate traffic to your device and deny all unwanted packets: http://www.cisco.com/warp/public/707/racl.html The following is the receive path ACL written to permit this type of traffic from trusted hosts: !--- Permit tcp services from trusted hosts allowed to the RP. access-list 151 permit tcp TRUSTED_ADDRESSES MASK any !--- Deny tcp services from all other sources to the RP. access-list 151 deny tcp any any !--- Permit all other traffic to the RP. access-list 151 permit ip any any !--- Apply this access list to the 'receive' path. ip receive access-list 151Control Plane Policing (CoPP) The Control Plane Policing (CoPP) feature may be used to mitigate this vulnerability. In the following example, only TCP traffic from trusted hosts and with 'receive' destination IP addresses is permitted to reach the route processor (RP). All other 'transit' IP traffic is unaffected. It should be noted that dropping traffic from unknown or untrusted IP addresses may affect hosts with dynamically assigned IP addresses from connecting to the Cisco IOS device. access-list 152 deny tcp TRUSTED_ADDRESSES MASK any access-list 152 permit tcp any any access-list 152 deny ip any any ! class-map match-all permit-tcp-class match access-group 152 ! ! policy-map permit-tcp-policy class permit-tcp-class drop ! control-plane service-policy input permit-tcp-policyIn the above CoPP example, the ACL entries that match the exploit packets with the "permit" action result in these packets being discarded by the policy-map "drop" function, while packets that match the "deny" action are not affected by the policy-map drop function. Please note that in the 12.2S and 12.0S Cisco IOS trains the policy-map syntax is different: policy-map permit-tcp-policy class class permit-tcp-class police 32000 1500 1500 conform-action drop exceed-action dropCoPP is available in Cisco IOS release trains 12.0S, 12.2SX, 12.2S, 12.3T, 12.4, and 12.4T. Additional information on the configuration and use of the CoPP feature can be found at the following URL: http://www.cisco.com/en/US/products/ps6642/products_white_paper0900aecd804fa16a.shtml Anti-spoofing The Unicast Reverse Path Forwarding (Unicast RPF or uRPF) feature helps to mitigate problems that are caused by spoofed IP source addresses. It is available on Cisco routers and firewalls. For further details, please refer to: http://www.cisco.com/en/US/partner/products/ps6441/products_command_reference_chapter09186a00804ae49f.html#wp1229984 By enabling Unicast Reverse Path Forwarding (uRPF), all spoofed packets will be dropped at the first device. To enable uRPF, use the following commands. router(config)#ip cef router(config)#interface interface # router(config-if)#ip verify unicast source reachable-via rx BGP and BTSH/GTSM Depending on your release of software, it may be possible to protect your BGP sessions from this memory leak. With the introduction of CSCee73956 ( registered customers only) , Cisco IOS has improved support for BTSH (BGP TTL Security Hack) to reduce, if not eliminate a risk of a memory leak due to this vulnerability. This functionality is also known as GTSM (Generalized TTL Security Mechanism) and documented in RFC 3682. This section refers to GTSM as applied to eBGP sessions only. Releases of Cisco IOS that contain CSCee73956 are protected from this attack against the BGP port (TCP port 179) only. Other ports should be protected accordingly. BTSH is not supported for iBGP sessions. BTSH was first introduced in Cisco IOS in 12.0(27)S, 12.3(7)T and 12.2(25)S. Note that the BTSH feature prior to CSCee73956 will not protect against this vulnerability. For more information on BTSH, please see: http://www.cisco.com/univercd/cc/td/doc/product/software/ios123/123newft/123t/123t_7/gt_btsh.htm BGP and MD5 Configuring your Cisco IOS device for BGP MD5 authentication is a valid workaround to help protect the vulnerable device from crafted TCP packets sent against the BGP port (TCP 179). This can be configured as shown in the following example: router(config)#router bgp router(config-router)#neighbor password It may be necessary to configure the same shared MD5 secret on both peers and at the same time. The introduction of CSCdx23494 ( registered customers only) will allow dynamically changing BGP MD5 keys without tearing the BGP session down. Although the BGP session will not be reset, BGP updates will not be processed until the same MD5 key is configured on both sides. Prior to the introduction of CSCdx23494 ( registered customers only) , failure to change the MD5 passwords at the same time will break the existing BGP session, and the new session will not get established until the exact same MD5 shared secret is configured on both devices. For a detailed discussion on how to configure BGP, refer to the following document: http://www.cisco.com/en/US/products/sw/iosswrel/ps1828/products_configur ation_guide_chapter09186a00800ca571.html Once the MD5 shared secret is configured, it is prudent to change it periodically. The exact period of time must fit within your company security policy. 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 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/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. 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 TAC. 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 discovered by Cisco during our internal testing process. 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://www.cisco.com/warp/public/707/cisco-sa-20070124-crafted-tcp.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 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 1.1 2007-January-30 BGP and MD5 update. 1.0 2007-January-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. [***** End Cisco Security Advisory Document ID: 72318 *****] _______________________________________________________________________________ CIAC wishes to acknowledge the contributions of Cisco 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. CIAC can be contacted at: Voice: +1 925-422-8193 (7x24) FAX: +1 925-423-8002 STU-III: +1 925-423-2604 E-mail: ciac@ciac.org Previous CIAC notices, anti-virus software, and other information are available from the CIAC Computer Security Archive. World Wide Web: http://www.ciac.org/ Anonymous FTP: ftp.ciac.org PLEASE NOTE: Many users outside of the DOE, ESnet, and NIH computing communities receive CIAC bulletins. If you are not part of these communities, please contact your agency's response team to report incidents. Your agency's team will coordinate with CIAC. The Forum of Incident Response and Security Teams (FIRST) is a world-wide organization. A list of FIRST member organizations and their constituencies can be obtained via WWW at http://www.first.org/. This document was prepared as an account of work sponsored by an agency of the United States Government. 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. LAST 10 CIAC BULLETINS ISSUED (Previous bulletins available from CIAC) R-102: Vulnerability in Microsoft Outlook (925938) R-103: Vulnerability in Vector Markup Language (929969) R-104: Vulnerabilities in Microsoft Excel (927198) R-105: XFree86 and xorg-x11 Security Update R-106: libgsf Security Update R-107: HP OpenView Network Node Manager (OV NNM) Remote Unauthorized Execution of Arbitrary Code R-108: Security Vulnerability in Processing GIF Images in the Java Runtime Environment R-109: Security Vulnerabilities: Buffer Overrun in NetMail 3.52 R-110: eIQnetworks Enterprise SEcurity Analyzer Syslog Server Buffer Overflow R-111: Security Vulnerability in the Sun Ray Server Software Admin GUI