User impersonation due to incorrect handling of the login JWTGHSA-h77f-xxx7-4858
HIGHFix: GeyserMC/Geyser@b954150GHSA-h77f-xxx7-4858 is a high-severity (CVSS 7.4) Improper Authentication vulnerability in org.geysermc:connector. A fix is available for org.geysermc:connector — see the affected versions and patch details below.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
GHSA-h77f-xxx7-4858 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.
Where this sits among everything scored
Of 385,738 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.
Real-World Exposure
org.geysermc:connectorReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Maven packages — download data is not available via public APIs for these ecosystems.
Description
Impact
<!--_What kind of vulnerability is it? Who is impacted?_-->This allows anyone that can connect to the server to forge a LoginPacket with manipulated JWT token allowing impersonation as any Bedrock user. Unless credentials are saved in your configuration, online mode is not affected as users are still required to log in separately. If your credentials are saved, there is no risk of exposing your email or password.
Patches
<!--_Has the problem been patched? What versions should users upgrade to?_-->This was patched as part of https://github.com/GeyserMC/Geyser/commit/b9541505af68ac7b7c093206ac7b1ba88957a5a6 and https://github.com/GeyserMC/Geyser/commit/ab2f5b326fe590e09167e8b45b4b165ac06ecd13. if your Geyser version is 1.4.2-SNAPSHOT or later, the issue has been addressed on your build.
Workarounds
<!--_Is there a way for users to fix or remediate the vulnerability without upgrading?_-->Geyser strongly recommends updating to fix this issue. If this isn't possible:
- Use online mode and don't save credentials in your Geyser configuration
- Use an additional authentication method on the Java server
References
<!--_Are there any links users can visit to find out more?_-->This was disclosed to us by a staff member over at Hive; you can read their disclosure here: https://updates.playhive.com/changelog/weekend-maintenance-breakdown
For more information
If you have any questions or comments about this advisory:
- Come talk to us over on our Discord server in the #development channel
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| ☕Maven | org.geysermc:connector | all versions | 1.4.2-SNAPSHOTorg.geysermc:connector:1.4.2-SNAPSHOT |
Affected Products
geysergeysermcDetection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for org.geysermc:connector, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update org.geysermc:connector to 1.4.2-SNAPSHOT or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-h77f-xxx7-4858 is resolved across your whole dependency graph.
Workarounds
Put an independent control in front of the weakness: restrict the affected endpoint or interface to trusted networks, require an additional authentication factor or proxy-level check, and invalidate existing sessions and credentials in case the flaw has already been used.
Frequently Asked Questions
Is GHSA-h77f-xxx7-4858 in your dependencies?
Find it across Maven, including transitive dependencies.