Half-Life client versions 1.1.1.0 and below (including all MODs based on the game, such as Counter-Strike and DoD) on Windows has a remote buffer overflow in the connection routine.
You can download this advisory from the following link: https://packetstormsecurity.com/files/download/31471/halflifeclient.txt
Source: https://packetstormsecurity.com/files/31471/halflifeclient.txt.html