You Can Now Run DOOM in DOOM

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You’ve heard of DOOM‘s incredible flexibility when it comes to installing the game in weird places. But did you ever imagine you would see DOOM in DOOM?

YouTuber and developer kgsws has found an exploit that allows DOOM (specifically the original DOOM 2 for DOS) to be hacked and another copy (Chocolate Doom, a source port) installed within the game. The result is that you can play DOOM within the world of DOOM.

I have found a code execution exploit in the original DOS Doom 2 and ported a Chocolate Doom to it. And then Chocolate Heretic. Attention: This does only work on the original DOS Doom2 version, no GZDoom or other source ports. This is a good thing as you don’t want code execution exploit on modern systems. People would abuse it to spread malicious code.

DOS version is available on Steam and you can use DosBox emulator to run it. Copy kgdid.wad to the directory where you have doom2.exe and then in DosBox start it with command “doom2 -file kgdid.wad”. (Copy other files too if you want to try them. Game injection has to be renamed to doomsav4.dsg)

The accompanying video explains how the code injection exploit was uncovered and how it can be used, but the bit you want to see starts at 8m 55s. At this point, kgsws explains:

Both games are running independent of each other that means you need double the memory. I would recommend you to get at least 16 megabytes of RAM. Now I can press F12 to control the other game it’s not just a cinema there’s no sound or music though but cheat works.

Obviously there is the potential here for some recursive madness which we would encourage you not to engage with. However, if you want to check out DOOM in DOOM yourself, grab it from the GitHub page.