CrashExploitFixer

This mod fixes a server crash exploit that has been bandaid-fixed by Mojang in Minecraft 1.21.1, which allows malicious players to crash a server immediately after joining it. It is currently estimated that this exploit is available on all versions back to 1.14.4!

If you are interested in the technical details of this exploit I recommend reading haykam's blogpost on the topic.

What Minecraft versions are affected?

All versions between 1.14.4 and 1.21 (inclusive) are confirmed to be affected. The issue was likely introduced in 17w45b, a 1.13 snapshot.

How hard is it to perform the exploit?

There has been some confusion on this. Mojang fixed two crash exploits in 1.21.1! One has been made very popular through a youtube video and has a lot of other cool exploits, but requires A LOT of complicated setup. The other exploit however allows anyone who has access to join a server (no permissions or anything required) to immediately crash it by sending one malicious packet!

I don't know you or your mods, how do I trust you?

I am trying to keep everything as transparent as possible.

• The project is open source and can be inspected on github

• The mod is very small, the entire patch logic lies within one small mixin and implements logic from paper that has already been tested on approximately 100.000 paper servers.

• The mod has already been successfully included in many major modpacks!