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Security Advisories: GSA_kwCzR0hTQS1oNzdmLXh4eDctNDg1OM0VmQ

User impersonation due to incorrect handling of the login JWT


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.


This was patched as part of and if your Geyser version is 1.4.2-SNAPSHOT or later, the issue has been addressed on your build.


Geyser strongly recommends updating to fix this issue. If this isn't possible:


This was disclosed to us by a staff member over at Hive; you can read their disclosure here:

For more information

If you have any questions or comments about this advisory:

Source: GitHub Advisory Database
Origin: Unspecified
Severity: High
Classification: General
Published: over 2 years ago
Updated: about 1 year ago

CVSS Score: 7.4
CVSS vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N

Identifiers: GHSA-h77f-xxx7-4858, CVE-2021-39177
References: Repository:
Blast Radius: 1.0

Affected Packages

Affected Version Ranges: <= 1.4.1-SNAPSHOT
Fixed in: 1.4.2-SNAPSHOT