Technical Cyber Security Alert TA06-081A – Sendmail contains a race condition caused by the improper handling of asynchronous signals. In particular, by forcing the SMTP server to have an I/O timeout at exactly the correct instant, an attacker may be able to execute arbitrary code with the privileges of the Sendmail process.
You can download this advisory from the following link: https://packetstormsecurity.com/files/download/44882/TA06-081A.txt
Source: https://packetstormsecurity.com/files/44882/Technical-Cyber-Security-Alert-2006-81A.html