Cisco Security Advisory – The Cisco IOS Intrusion Prevention System (IPS) feature contains a vulnerability in the processing of certain IPS signatures that use the SERVICE.DNS engine. This vulnerability may cause a router to crash or hang, resulting in a denial of service condition. Cisco has released free software updates that address this vulnerability. There is a workaround for this vulnerability.
You can download this advisory from the following link: https://packetstormsecurity.com/files/download/70287/cisco-sa-20080924-iosips.txt
Source: https://packetstormsecurity.com/files/70287/Cisco-Security-Advisory-20080924-iosips.html