Cisco routers vulnerable to DoS

Cisco has warned that vulnerabilities in its series 12000 routers may allow attackers to denial of service (DoS) the machines.

The company said that heavy scanning traffic on a network, perhaps initiated by a hacker, could saturate the router's CPU resources and cause the machine to fall over.

If there is no valid return path for packets recieved by the router, it is forced to send Internet Control Message Protocol (ICMP) Unreachable packets. Forcing the router to send a high number of these can slow it down or crash it altogether.

Sending fragmented data packets to a 12000 router will circumvent the machine's Access Control List, which is designed to stop malicious traffic, also leading to a potential DoS attack.

But Paul Cunningham, marketing director of specialist Cisco distributor, Comstor said: "Once these things are examined more closely, you usually find that there are pretty narrowly defined parameters in which these problems could become risks."

He added: "Cisco has a good track record in getting things fixed. It is always concerning when these things come up, but they [Cisco] do a good job in handling them."