-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 National Cyber Alert System Technical Cyber Security Alert TA05-210A Cisco IOS IPv6 Vulnerability Original release date: July 29, 2005 Last revised: -- Source: US-CERT Systems Affected * Cisco IOS devices with IPv6 enabled For specific information, please see the Cisco Advisory. Overview Cisco IOS IPv6 processing functionality contains a vulnerability that could allow an unauthenticated, remote attacker to execute arbitrary code or cause a denial of service. I. Description Cisco IOS contains a vulnerability in the way IPv6 packets are processed. US-CERT has not confirmed further technical details. According to the Cisco Advisory, this vulnerability could be exploited by an attacker on the same IP subnet: Crafted packets from the local segment received on logical interfaces (that is, tunnels including 6to4 tunnels) as well as physical interfaces can trigger this vulnerability. Crafted packets can not traverse a 6to4 tunnel and attack a box across the tunnel. The crafted packet must be sent from a local network segment to trigger the attack. This vulnerability can not be exploited one or more hops from the IOS device. US-CERT strongly recommends that sites running Cisco IOS devices review the Cisco Advisory and upgrade as appropriate. We are tracking this vulnerability as VU#930892. II. Impact This vulnerability could allow an unauthenticated, remote attacker on the same IP subnet to execute arbitrary code or cause a denial of service. The attacker may be able to take control of a vulnerable device. III. Solutions Upgrade Upgrade to a fixed version of IOS. Please see the Software Versions and Fixes section of the Cisco Advisory for details. Disable IPv6 From the Cisco Advisory: In networks where IPv6 is not needed, disabling IPv6 processing on an IOS device will eliminate exposure to this vulnerability. On a router which supports IPv6, this must be done by issuing the command "no ipv6 enable" and "no ipv6 address" on each interface. Appendix A. Vendor Information Cisco Systems, Inc. Cisco Systems, Inc. has released a security advisory regarding a vulnerability which was disclosed on July 27, 2005 at the Black Hat security conference. Security advisory is available at: http://www.cisco.com/warp/public/707/cisco-sa-20050729-ipv6.shtml For up-to-date information on security vulnerabilities in Cisco Systems, Inc. products, visit http://www.cisco.com/go/psirt. Appendix B. References * US-CERT Vulnerability Note VU#930892 - * Cisco Security Advisory: IPv6 Crafted Packet Vulnerability - _________________________________________________________________ Information regarding this vulnerability was primarily provided by Cisco Systems, who in turn acknowledge the disclosure of this vulnerability at the Black Hat USA 2005 Briefings. _________________________________________________________________ Feedback can be directed to US-CERT Technical Staff. Send mail to with "TA05-210A feedback VU#930892" in the subject. _________________________________________________________________ The most recent version of this document is available at: _________________________________________________________________ Produced 2005 by US-CERT, a government organization. _________________________________________________________________ Terms of use: _________________________________________________________________ Revision History July 29, 2005: Initial release -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.2.1 (GNU/Linux) iQEVAwUBQuqgLRhoSezw4YfQAQI5iwgAkSYXPNt6Hffg7BfMeYoBaZ4Co6XFVjQ6 nWHKt1inYcYta/DXEuWJAhcjI/t8v74OH0b5sxGEr0mwtzEwV2r5pAF6nQesqyoj q3r60OE3TZygxUZPrGNmmkSpkhoNap9cSVs97Xt6Fd4evOmp0VZ6pqMdJtQ/r5xk d67LicCM9NLNoC0LPoen2/7ICu7jqxZnoF4oHDkZS8b2g2mx7vfz3Htj44Nd5/eD tWe8HqF8ReSyLEiOj8z8vrjcfz+BIwSLXnyr6DDxSvFmhy0CunGFkCQq074CwbVE GZjAJSn2r/A2Pp3HBP/RxQ9BNv8rHrSF7DkG9gADc5PV8WpaLCHP0Q== =4jtB -----END PGP SIGNATURE-----