Cisco Security Advisory: Cisco routers and switches running the IOS software are vulnerable to a denial of service attack. A rare sequence of crafted IPv4 packets sent directly to the device may cause the input interface to stop processing traffic once the input queue is full.
You can download this advisory from the following link: https://packetstormsecurity.com/files/download/31387/ciscoIPv4.txt
Source: https://packetstormsecurity.com/files/31387/ciscoIPv4.txt.html