3proxy suffers from a double free vulnerability that can cause instability and potentially crash a service. Versions 0.5.3i and below are vulnerable.
You can download this advisory from the following link: https://packetstormsecurity.com/files/download/60343/AD-LAB-07006.txt
Source: https://packetstormsecurity.com/files/60343/AD-LAB-07006.txt.html