Vulnerability GHSA-7hmv-4j2j-pp6f

Impact

The server handles ActorEventPacket to trigger consuming animations from vanilla clients when they eat food or drink potions.

This can be abused to make the server spam other clients, and to waste server CPU and memory. For every ActorEventPacket sent by the client, an animation event will be sent to every other player the attacker is visible to.

This is similar to various other vulnerabilities which were fixed in the network overhaul of PM4 (e.g. AnimatePacket and LevelSoundEventPacket), but somehow this one slipped through the net.

Patches

The problem was addressed in aeea1150a772a005b92bd418366f1b7cf1a91ab5 by changing the mechanism for consuming animations to be fully controlled by the server. ActorEventPacket from the client is now discarded.

Workarounds

A plugin could use DataPacketDecodeEvent to rate-limit ActorEventPacket to prevent the attack.