cve.bz

CVE-2021-39177

9.8 criticalEPSS 1.4%

Critical (9.8) in geysermc geyser. EPSS 1.4% chance of exploitation in the next 30 days. Fixed in org.geysermc:connector 1.4.2-SNAPSHOT.

Geyser is a bridge between Minecraft: Bedrock Edition and Minecraft: Java Edition. Versions of Geyser prior to 1.4.2-SNAPSHOT allow anyone that can connect to the server to forge a LoginPacket with manipulated JWT token allowing impersonation as any user. Version 1.4.2-SNAPSHOT contains a patch for the issue. There are no known workarounds aside from upgrading.

Severity

CVSS 3.1

9.8 critical
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
EPSS
1.4% chance of exploitation in the next 30 days; higher than 73% of CVEs (scores of 2026-11-01)
CWE
CWE-287
Published
Modified
Record from
the NVD, synced

Affected

Packages (OSV)

AdvisoryEcosystemPackageAffectedFixed in
GHSA-h77f-xxx7-4858Mavenorg.geysermc:connector<1.4.2-SNAPSHOT1.4.2-SNAPSHOT

References

Check your stackJSON