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Status published
High
CVE-2021-39177
User impersonation due to incorrect handling of the login JWT
Vulnerability 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.
Impact Analysis
Refer to official advisory for detailed impact metrics.
Remediation
Ensure systems are updated to the latest vendor-supplied patch levels.
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Credits & Attribution
No credits recorded in the NVD database.
Affected Vendor
GeyserMC
View all reports →Affected Software
Geyser
Vulnerable Versions:
<= 1.4.1-SNAPSHOT
Timeline
Official Publish:
August 30th, 2021
Last Modified:
August 4th, 2024
Added to House:
July 21st, 2026
CVSS Vectors
V3:
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N