Cisco Security Advisory – The Intrusion Prevention System (IPS) feature set of Cisco IOS contains several vulnerabilities. These include a flaw where fragmented IP packets may be used to evade signature inspection and another flaw where IPS signatures utilizing the regular expression feature of the ATOMIC.TCP signature engine may cause a router to crash resulting in a denial of service.
You can download this advisory from the following link: https://packetstormsecurity.com/files/download/54410/cisco-sa-20070213-iosips.txt
Source: https://packetstormsecurity.com/files/54410/Cisco-Security-Advisory-20070213-iosips.html