Cisco Security Advisory – Cisco Internetwork Operating System (IOS) Software is vulnerable to a Denial of Service (DoS) and potentially an arbitrary code execution attack from a specifically crafted IPv6 packet. The packet must be sent from a local network segment. Only devices that have been explicitly configured to process IPv6 traffic are affected. Upon successful exploitation, the device may reload or be open to further exploitation.
You can download this advisory from the following link: https://packetstormsecurity.com/files/download/39010/cisco-sa-20050729-ipv6.txt
Source: https://packetstormsecurity.com/files/39010/Cisco-Security-Advisory-20050729-ipv6.html