[ISN] Jumbo bug crashes Cisco anti-hacker appliances

From: InfoSec News (alerts@private)
Date: Fri Jun 20 2008 - 01:05:08 PDT


By John Leyden
The Register
19th June 2008

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.

Jumbo Ethernet is a data center technology designed to increase 
inter-server communication performance. By increasing the size of frames 
less effort is expending on unpacking packets in the same way it's 
easier to deal with one big envelope containing a wad of papers rather 
than a larger number of smaller letters. The technology, designed for 
hi-speed LANs, is not supported by default on Cisco routers or switches.

The vulnerability was reported to Cisco by HD Moore of Metasploit fame. 
There's no evidence that the flaw has been used in anger by hackers. 
Nonetheless sys admin would be prudent to patch vulnerable IPS systems, 
especially in the absence of any temporary fixes (workarounds).

The issue is explained in greater detail in Cisco's advisory here [1].

[1] http://www.cisco.com/warp/public/707/cisco-sa-20080618-ips.shtml

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