# CVE-2026-86200: PocketMine-MP denial of service in LoginPacket handler

Source: https://junglewise.ai/threats/cve-2026-86200-pocketmine-mp-denial-of-service-in-loginpacket-handler  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-09-09. Updated: 2026-09-26  
License: CC BY 4.0 with a link back

CVE-2026-86200 · Severity: medium · CVSS 5.3 · Published 2026-09-09

PocketMine-MP is a server software for Minecraft Pocket Edition games. A vulnerability in the login packet handler allows remote attackers to send specially crafted login requests with excessive junk data, causing the server to waste CPU time logging warnings and degrading performance for legitimate players.

Technologies: [pocketmine/pocketmine-mp (Packagist)](https://junglewise.ai/threats/technologies/pocketmine-pocketmine-mp). Vendors: [Packagist](https://junglewise.ai/threats/vendors/packagist).

## Quick answers

**Is CVE-2026-86200 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-86200 being exploited in the wild.

**How severe is CVE-2026-86200?** Medium severity, with a CVSS score of 5.3, published 9 September 2026.

**Which products and versions are affected?** pocketmine/pocketmine-mp (Packagist) ECOSYSTEM:introduced=0,fixed=5.42.1.

**Is there a fix for CVE-2026-86200?** Yes. pocketmine/pocketmine-mp (Packagist): upgrade to 5.42.1 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-86200 attacked?** It is attacked over the network, in a hosted service.

**Am I affected by CVE-2026-86200?** Check whether you run pocketmine/pocketmine-mp (Packagist) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- pocketmine/pocketmine-mp (Packagist): upgrade to 5.42.1 or later

  ```sh
  composer require pocketmine/pocketmine-mp:^5.42.1
  ```


## Technical details

The vulnerability is a denial-of-service condition in the LoginPacket handler where the JsonMapper instance processes the clientData JWT with a configuration that warns on unexpected properties instead of rejecting them. Remote attackers can craft malicious login packets containing large numbers of junk properties in the JWT body, causing the server to flood warning messages and waste CPU cycles. The attack requires network access to the server's login endpoint and no authentication. The fix, deployed in version 5.42.1, restricts unknown properties to a maximum of 10 and rejects packets exceeding this limit while maintaining compatibility with legitimate JWT variations from Microsoft.

## Affected products

- PocketMine Project PocketMine-MP before 5.42.1

## Identifiers

- CVE-2026-86200
- GHSA-xp4f-g2cm-rhg7

## Timeline

- 2026-04-14: disclosed: GitHub security advisory GHSA-xp4f-g2cm-rhg7 published
- 2026-05-09: patched: Fix deployed in commit c1d4a81, version 5.42.1
- 2026-09-09: advisory: CVE-2026-86200 published

## References

- [https://github.com/pmmp/PocketMine-MP/commit/c1d4a813fb8c21bfd8b9affd040da864b794df71](https://github.com/pmmp/PocketMine-MP/commit/c1d4a813fb8c21bfd8b9affd040da864b794df71)
- [https://github.com/pmmp/PocketMine-MP/security/advisories/GHSA-xp4f-g2cm-rhg7](https://github.com/pmmp/PocketMine-MP/security/advisories/GHSA-xp4f-g2cm-rhg7)

## Related threats

- [PocketMine-MP denial of service in ModalFormResponsePacket handling](https://junglewise.ai/threats/cve-2026-86204-pocketmine-mp-denial-of-service-in-modalformresponsepacket)
- [PocketMine-MP item duplication via despawn entity attack race condition](https://junglewise.ai/threats/cve-2026-86203-pocketmine-mp-item-duplication-via-despawn-entity-attack-race)
- [PocketMine-MP network amplification in ActorEventPacket](https://junglewise.ai/threats/cve-2026-86202-pocketmine-mp-network-amplification-in-actoreventpacket)
- [PocketMine-MP denial of service in LoginPacket processing](https://junglewise.ai/threats/cve-2026-86201-pocketmine-mp-denial-of-service-in-loginpacket-processing)
- [PocketMine-MP improper validation of ResourcePackClientResponsePacket](https://junglewise.ai/threats/cve-2026-86198-pocketmine-mp-improper-validation-of)