Summary
PocketMine-MP vulnerable to server crash with certain invalid JSON payloads in LoginPacket due to vulnerable dependency
Workarounds
- Users of PocketMine-MP source installations may manually install the patched version of JsonMapper by backporting commit pmmp/PocketMine-MP@09668a37d66c6023685a948b7550c918620e98f2.
- A plugin may also be able to workaround this issue by using
DataPacketReceiveEventto attempt detection of suspicious payloads. AnErrorExceptionwill be thrown in the crash case, which can be caught by plugins.
References
cweiske/jsonmapper#210
Impact
An attacker could crash PocketMine-MP by sending malformed JSON in LoginPacket.
This happened due to a bug in netresearch/jsonmapper. The library wasn't doing proper checks when mapping JSON arrays and objects onto scalar model properties such as strings.
GHSA-PQP3-8RRW-G8VM has a CVSS score of 7.5 (High). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (4.20.5, 4.21.1); upgrading removes the vulnerable code path.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
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The problem was fixed in a fork of JsonMapper in dktapps/JsonMapper@a31902a31f5b6fdb832f57c0e3a3f16a3b41c012. PocketMine-MP releases 4.20.5 and 4.21.1 have been released with the fix.
Frequently Asked Questions
- What is GHSA-PQP3-8RRW-G8VM? GHSA-PQP3-8RRW-G8VM is a high-severity security vulnerability in pocketmine/pocketmine-mp (composer), affecting versions < 4.20.5. It is fixed in 4.20.5, 4.21.1.
- How severe is GHSA-PQP3-8RRW-G8VM? GHSA-PQP3-8RRW-G8VM has a CVSS score of 7.5 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
- Which versions of pocketmine/pocketmine-mp are affected by GHSA-PQP3-8RRW-G8VM? pocketmine/pocketmine-mp (composer) versions < 4.20.5 is affected.
- Is there a fix for GHSA-PQP3-8RRW-G8VM? Yes. GHSA-PQP3-8RRW-G8VM is fixed in 4.20.5, 4.21.1. Upgrade to this version or later.
- Is GHSA-PQP3-8RRW-G8VM exploitable, and should I be worried? Whether GHSA-PQP3-8RRW-G8VM is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether GHSA-PQP3-8RRW-G8VM is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix GHSA-PQP3-8RRW-G8VM?
- Upgrade
pocketmine/pocketmine-mpto 4.20.5 or later - Upgrade
pocketmine/pocketmine-mpto 4.21.1 or later
- Upgrade