Executive brief
PocketMine-MP is a Minecraft server software that processes login requests from players. A vulnerability in how login packet JSON data is parsed allows a remote attacker to crash the server by sending malformed JSON, causing service outages for all connected players.
Technical details
The vulnerability is a denial of service flaw in the LoginPacket JSON processing logic, specifically in the JsonMapper used during login handling. Attackers can send malformed JSON data that exploits improper object initialization from scalar JSON types, triggering unset required properties and causing an application crash. The attack is network-accessible and requires no authentication. A fix is available in version 5.11.1 and later, as evidenced by the hardening commit to the JsonMapper login JSON handling.
Affected products
- PocketMine PocketMine-MP before 5.11.1
Timeline
- 2026-09-09: disclosed
- 2026-09-09: patched: Fixed in version 5.11.1 via hardened JsonMapper on login JSON handling