Jumbo bug crashes Cisco anti-hacker appliances

Security appliances from Cisco can crash when handling Jumbo Ethernet frames, the networking giant warned on Wednesday.

Cisco has published a software patch designed to address a denial of service vulnerability in its Intrusion Prevention System (IPS) appliances. IPS systems are designed to block common hacker attacks and exploits. But a bug in the devices meant that "kernel panic" leading to a crash might be induced when processing Jumbo Ethernet packets.

Recovery in these cases would involve resetting the devices using a power cycle. In the meantime network traffic would be cut off except in the case of Cisco's 4260 and 4270 IPS platforms, which have the option to allow traffic to bypass devices in the event of a system failure.

The flaw only applies where Cisco IPS platforms have Gigabit network interfaces installed and where these are deployed in inline mode. The flaw becomes a moot point in slower speed networks or where IPS devices are configured just to sniff traffic (promiscuous mode), where they essentially act as hi-tech burglar alarms.