Vulnerability · Published Aug 30, 2021 · Assigned by GitHub_M

CVE-2021-39177User impersonation due to incorrect handling of the login JWT

High 7.4

In plain English

A high-severity improper authentication in Geyser from GeyserMC. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 1.4% (higher than 73% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)7.4High

Exploit odds (30 days)1.4%top 26.6% of all CVEs

Exploited in the wildNo reportsnot in CISA KEV

Attack toolingNoneno public tooling known

Official description

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.

Affected packages & fixed versions

Ecosystem	Package	Fixed in	Advisory
Maven	org.geysermc:connector	1.4.2-SNAPSHOT	GHSA-h77f-xxx7-4858

Affected products (as reported)

Vendor	Product	Versions
GeyserMC	Geyser	<= 1.4.1-SNAPSHOT

Weakness: CWE-287 · Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N

References

https://github.com/GeyserMC/Geyser/security/advisories/GHSA-h77f-xxx7-4858 x_refsource_CONFIRM
https://github.com/GeyserMC/Geyser/commit/b9541505af68ac7b7c093206ac7b1ba88957a5a6 x_refsource_MISC
https://updates.playhive.com/weekend-maintenance-disclosure-2kJMaY x_refsource_MISC