The whole process, from initial email to fix, lasted less than 30 days. I would like to extend my thanks to the Valve Security team and specifically to Alfred Reynolds who was my liaison during the disclosure process. The vulnerability discussed in this article has been disclosed to Valve Security and the patch publicly deployed on July 10th. This automatic resource fetching looked like the ticket to a remotely exploitable vulnerability via a local file. Only then will the client begin receiving commands and entity updates from the server.

Once all of the resources have been downloaded, they have to be loaded and parsed from disk into memory. Upon connecting to the server, the game client will automatically download any required resources (maps, textures, sounds, etc.). What makes Counter Strike an interesting target is that it relies on a game lobby for players to find and select servers to play on. Condition Zero, Half-Life 1, and CS 1.6 all run on the GoldSrc engine, which was created by Valve and is based upon the original Quake engine. One night while playing Counter Strike: Condition Zero (CZ), I decided to take a break and challenge myself to find an exploitable bug in the old engine known as GoldSrc.

Cs go crashes on map load