Half-Life server versions 1.1.1.0 and below (including all MODs based on the game, such as Counter-Strike and DoD) on both Windows and Linux suffer from a remote buffer overflow and are vulnerable to a denial of service attack. Affects both the game and dedicated servers.
You can download this advisory from the following link: https://packetstormsecurity.com/files/download/31469/halflife.txt
Source: https://packetstormsecurity.com/files/31469/halflife.txt.html