A weakness has been reported in Cisco Catalyst 6500 and Cisco 7600 series devices, which can be exploited by malicious people to bypass certain security restrictions.

The problem is that packets destined for the 127.0.0.0/8 network may be received and processed by e.g. the Supervisor module or Multilayer Switch Feature Card (MSFC). This can be exploited to e.g. bypass existing access control lists.

Successful exploitation requires that systems are running Hybrid Mode (Catalyst OS (CatOS) software on the Supervisor Engine and IOS Software on the MSFC) or Native Mode (IOS Software on both the Supervisor Engine and the MSFC).

The weakness is reported in all software versions on Cisco Catalyst 6500 and Cisco 7600 series prior to 12.2(33)SXH.

Solution
Update to 12.2(33)SXH.

Provided and/or discovered by
The vendor credits Lee E. Rian.

Changelog
Further details available to Secunia VIM customers

Original Advisory
Cisco:
http://www.cisco.com/warp/public/707/cisco-sr-20070926-lb.shtml

Deep Links
Links available to Secunia VIM customers