Cisco flags DoS security alert

By Alun Williams

Posted on 17 Jul 2003 at 16:02

Cisco Systems has issued a security advisory for Cisco IOS, its widely-deployed network operating system.

A vulnerability has been discovered for devices running IOS, such as routers and switches. Cisco reports that specially crafted IPv4 packets can be sent to devices that stops them processing other packets on that interface. The attack is silent but deadly as no alarms will be triggered and nor will the router reload to correct itself.

It seems a particular sequence of IPv4 packets received by the processor on a Cisco IOS device may force the device to flag the input queue on an interface as full and stop processing inbound traffic.

More details and patch information can be found in the advisory on the Cisco website

Cisco devices that do not run Cisco IOS software and devices that run only Internet Protocol version 6 (IPv6) are not affected.