-----BEGIN PGP SIGNED MESSAGE----- =============================================================================== CA-93:07 CERT Advisory April 22, 1993 Cisco Router Packet Handling Vulnerability - ----------------------------------------------------------------------------- The CERT Coordination Center has received information indicating that under some circumstances Cisco routers will pass IP source routed packets which should have been denied. Routers which do not use the "no ip source-route" command are not affected. This vulnerability applies to all models of Cisco routers. This problem occurs with the following releases of software: 8.2, 8.3, 9.0, 9.1 and 9.17. Cisco Systems and CERT recommend that sites using Cisco routers to provide firewall protection take action to eliminate this vulnerability from their networks. This security issue is fixed in Cisco software releases 8.3(7.2), 9.0(5), 9.1(4) 9.17(2.1) and in all later releases. Customers who are using software release 8.2 must upgrade to a later release and should contact Cisco's Technical Assistance Center (TAC) at 800-553-2447 (Internet: tac@cisco.com) for more information. Cisco recommends that customers whose routers may be affected by this vulnerability upgrade their software to the following versions: Release (Update) 8.3 (8) 9.0 (5) 9.1 (4) 9.17 (3) These releases are available on Cisco's Customer Information On-Line (CIO) service for those customers having a maintenance contract. Other customers may obtain these releases through Cisco's Technical Assistance Center or by contacting their local Cisco distributor. - ----------------------------------------------------------------------------- I. Description A vulnerability exists in Cisco routers such that a router which is configured to suppress source routed packets with the following command: no ip source-route may allow traffic which should be suppressed. II. Impact This vulnerability can allow unauthorized traffic to pass through the router/gateway. III. Solution Cisco recommends that affected customers upgrade to a later version. Customers who cannot upgrade immediately may be able use access lists to prevent unauthorized traffic. Customers who have questions should contact the Cisco Technical Assistance Center at 800-553-2447 for assistance. Internet: tac@cisco.com - --------------------------------------------------------------------------- The CERT Coordination Center wishes to thank Cisco Systems for responding to this problem. - --------------------------------------------------------------------------- If you believe that your system has been compromised, contact the CERT Coordination Center or your representative in FIRST (Forum of Incident Response and Security Teams). Internet E-mail: cert@cert.org Telephone: 412-268-7090 (24-hour hotline) CERT personnel answer 8:30 a.m.-5:00 p.m. EST(GMT-5)/EDT(GMT-4), and are on call for emergencies during other hours. CERT Coordination Center Software Engineering Institute Carnegie Mellon University Pittsburgh, PA 15213-3890 Past advisories, information about FIRST representatives, and other information related to computer security are available for anonymous FTP from cert.org (192.88.209.5). -----BEGIN PGP SIGNATURE----- Version: 2.6.2 iQCVAwUBMaMxLXVP+x0t4w7BAQGXWQP+N5ZtvBIROzN4KdLUNfxL8swx7jHpRvbp uNulOwQ7KAIi6D20FvEdJ14XKOQPi5UVmPBEUwwAiD8XltAK4+BkdhoJrqVqLAau i8A/4UP5MnTWKnGgSgMWb3Si/EXFKD2Z7imWnEPK8Tah42Omj5em4PA8UAN632sr MlwGuIAfTi4= =ZdlI -----END PGP SIGNATURE-----