{"cve":"CVE-2021-39177","nvd":{"published":"2021-08-30T23:15:07.070","modified":"2026-06-17T04:03:15.263","status":"Modified","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.","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","score":9.8},"cwes":["CWE-287"],"references":["https://github.com/GeyserMC/Geyser/commit/b9541505af68ac7b7c093206ac7b1ba88957a5a6","https://github.com/GeyserMC/Geyser/security/advisories/GHSA-h77f-xxx7-4858","https://updates.playhive.com/weekend-maintenance-disclosure-2kJMaY","https://github.com/GeyserMC/Geyser/commit/b9541505af68ac7b7c093206ac7b1ba88957a5a6","https://github.com/GeyserMC/Geyser/security/advisories/GHSA-h77f-xxx7-4858"],"products":["geysermc:geyser"],"source":"nvd","synced_at":"2026-10-19T21:21:57.125947417+00:00"},"epss":{"cve":"CVE-2021-39177","score":0.01443,"percentile":0.73248,"date":"2026-11-01"},"kev":null,"osv":[{"id":"GHSA-h77f-xxx7-4858","url":"https://osv.dev/vulnerability/GHSA-h77f-xxx7-4858","summary":"User impersonation due to incorrect handling of the login JWT","modified":"2026-10-01T18:45:07.632931777Z","packages":[{"ecosystem":"Maven","name":"org.geysermc:connector","purl":"pkg:maven/org.geysermc/connector","ranges":["<1.4.2-SNAPSHOT"],"fixed":["1.4.2-SNAPSHOT"]}]}],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}