Hi, I'm one of the developers for Team Fortress 2 Classic, a source mod project. Recently, someone abused a bug present in Source SDK 2013 MP to distribute viruses to quite a few of our players and developers. The way they did it was by abusing a spray exploit present in the SDK 2013 MP edition to upload a file pretending to be a spray to all players and executing it. The technical info on how it works from one of our other coders will be posted at the end of this email, but here's what you need to know as a server owner:
We don't know how many source games are vulnerable. The big name VALVe ones aren't, but any sourcemod probably is. This includes ones on steam like Fortress Forever, or Fistful of Frags. If you're running a server for a non-VALVe or bigname(Titanfall, GMOD, etc.) Source Engine game, then here's what you need to do: 1. Set sv_upload to 0 on your server. 2. If you are a TF2C server host, shut your server down and start scanning your server for viruses. 3. Pester valve to fix this ASAP. TL;DR: Sprays can be exploited to run code on people's systems and break into accounts, we've had quite a few CS:GO and TF2 items lifted from accounts and moved to trade alts and disappearing after that. Disable sprays ASAP if you host a sourcemod multiplayer server. Here's the technical info for how stuff works: "The vulnerability is triggered by a missing check to see if a memory allocation succeded in the loading of VTFs. When the material is loaded, there is space allocated for the material. The crucial option in the using of this exploit is the option to skip Mipmaps from the material. If, for instance, the first mipmap is skipped, the game will copy the mipmap data to buffer + size of first mipmap. When the memory allocation fails, the buffer will be 0, because thats what malloc returns on out of memory. This means, that the only factor determining where the block is put is determined by the size of the first mipmap. This way you can put the data in the second mipmap whereever you want, meaning you can write to a predictable location in memory. This is additionally encouraged due to the fact that ASLR is disabled for the module in question. From that point on ROP is used to mark a controlled memory location executable and transfer control to it, bypassing DEP. The distribution of the malicious material file can be easily done through the use of the spray system, which uploads a custom material to the server and distributes it. This is of course not the only way to distribute it, but one used in this case. This is not absolutely accurate and technical details have been left out due to them not influencing this exploit."
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