Crytek. The 37MB download fixes a security hole in the game which caused client and server crashes during online games. You'll need patch 1.2 installed before updating to 1.2.1. The update also has word on new documentation for server operators for the game.
The highly anticipated hotfix for Crysis has been approved and is now ready for distribution. The 37MB sized patch for Crysis fixes the known security hole in the game code which causes client and server crashes when playing online.
Be sure that you have patch 1.2 installed before, since this is required to apply the hotfix to your Crysis installation.
Added "Basic Setup" section (beginners guide how to get the server running with the least amount of work)