Secunia

Cisco has reported a vulnerability in CatOS for various Catalyst switches, which can be exploited by malicious people to cause a DoS (Denial of Service) on certain active services on a vulnerable device.

The vulnerability is caused due to an error in the handling of certain TCP packets. This can be exploited by making just eight (8) TCP connection attempts with a non-standard TCP flag combination to a listening service. After receiving the connection attempts, the service will stop responding to further connection attempts.

The vulnerability has been reported to affect the following Catalyst models:
- Catalyst 4000 Series including models 2948G and 2980G/2980G-A
- Catalyst 5000 Series including models 2901, 2902 and 2926
- Catalyst 6000

Solution
Cisco has released upgraded CatOS versions. A patch matrix is available at the web page (in the "Software Versions and Fixes" section) referenced in "Original Advisory".
Original Advisory
http://www.cisco.com/warp/public/707/cisco-sa-20030709-swtcp.shtml

Deep Links
Links available in Customer Area