{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-55165","assignerOrgId":"a0819718-46f1-4df5-94e2-005712e83aaa","state":"PUBLISHED","assignerShortName":"GitHub_M","dateReserved":"2026-06-16T15:13:28.165Z","datePublished":"2026-08-18T18:49:59.538Z","dateUpdated":"2026-08-18T19:35:55.129Z"},"containers":{"cna":{"title":"Lemur : JWT verifier trusts attacker-supplied alg from token header — defense-in-depth gap; chain-dependent ATO with secret disclosure","problemTypes":[{"descriptions":[{"cweId":"CWE-347","lang":"en","description":"CWE-347: Improper Verification of Cryptographic Signature","type":"CWE"}]}],"metrics":[{"cvssV3_1":{"attackComplexity":"HIGH","attackVector":"NETWORK","availabilityImpact":"NONE","baseScore":4.8,"baseSeverity":"MEDIUM","confidentialityImpact":"LOW","integrityImpact":"LOW","privilegesRequired":"NONE","scope":"UNCHANGED","userInteraction":"NONE","vectorString":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N","version":"3.1"}}],"references":[{"name":"https://github.com/Netflix/lemur/security/advisories/GHSA-r9gp-7f88-9r54","tags":["x_refsource_CONFIRM"],"url":"https://github.com/Netflix/lemur/security/advisories/GHSA-r9gp-7f88-9r54"},{"name":"https://github.com/Netflix/lemur/commit/89898e665beed044cf7bd5927dfaa484e55bf242","tags":["x_refsource_MISC"],"url":"https://github.com/Netflix/lemur/commit/89898e665beed044cf7bd5927dfaa484e55bf242"},{"name":"https://github.com/Netflix/lemur/releases/tag/v1.9.2","tags":["x_refsource_MISC"],"url":"https://github.com/Netflix/lemur/releases/tag/v1.9.2"}],"affected":[{"vendor":"Netflix","product":"lemur","versions":[{"version":"< 1.9.2","status":"affected"}]}],"providerMetadata":{"orgId":"a0819718-46f1-4df5-94e2-005712e83aaa","shortName":"GitHub_M","dateUpdated":"2026-08-18T18:49:59.538Z"},"descriptions":[{"lang":"en","value":"Lemur manages TLS certificate creation. Prior to 1.9.2, the JWT verifier in lemur/auth/service.py:130-137 used fetch_token_header to read header_data[\"alg\"] from an unverified token and passed that attacker-controlled value to decode_with_multiple_secrets. PyJWT 2.x rejects alg=none with the configured key, so the flaw is a defense-in-depth gap rather than a direct authentication bypass in the shipped configuration. The unpinned algorithm can become exploitable after an asymmetric-signing migration through algorithm confusion, and it weakens algorithm-based anomaly detection because the token chooses the recorded value. A separate disclosure of LEMUR_TOKEN_SECRET would also permit forged HS256 tokens, although that disclosure is an independent prerequisite. The fix introduces the server-controlled LEMUR_TOKEN_ALGORITHMS allowlist and defaults it to HS256. This issue is fixed in version 1.9.2."}],"source":{"advisory":"GHSA-r9gp-7f88-9r54","discovery":"UNKNOWN"}},"adp":[{"references":[{"url":"https://github.com/Netflix/lemur/security/advisories/GHSA-r9gp-7f88-9r54","tags":["exploit"]}],"metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2026-08-18T19:35:36.998493Z","id":"CVE-2026-55165","options":[{"Exploitation":"poc"},{"Automatable":"no"},{"Technical Impact":"partial"}],"role":"CISA Coordinator","version":"2.0.3"}}}],"title":"CISA ADP Vulnrichment","providerMetadata":{"orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","shortName":"CISA-ADP","dateUpdated":"2026-08-18T19:35:55.129Z"}}]}}