{"id":"CVE-2026-55165","title":"Lemur manages TLS certificate creation","summary":"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_wit…","severity":"medium","cvss":4.8,"cvssVector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N","cwe":["CWE-347"],"vendor":"lemur","product":"lemur","affected":["lemur < 1.9.2"],"patched":["lemur 1.9.2"],"published":"2026-08-18","updated":"2026-09-08","sourceUpdated":"2026-09-08T21:02:26.047","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-55165","references":[{"url":"https://github.com/Netflix/lemur/commit/89898e665beed044cf7bd5927dfaa484e55bf242","label":"security-advisories@github.com"},{"url":"https://github.com/Netflix/lemur/releases/tag/v1.9.2","label":"security-advisories@github.com"},{"url":"https://github.com/Netflix/lemur/security/advisories/GHSA-r9gp-7f88-9r54","label":"security-advisories@github.com"},{"url":"https://github.com/Netflix/lemur/security/advisories/GHSA-r9gp-7f88-9r54","label":"134c704f-9b21-4f2e-91b3-4a467353bcc0"},{"url":"https://github.com/advisories/GHSA-r9gp-7f88-9r54"}],"tags":["nvd","ghsa","pip"],"epss":0.00154,"epssPercentile":0.04867,"ecosystem":"pip","ingestedAt":"2026-06-26T16:43:14.204Z","slug":"CVE-2026-55165","body":"## Overview\n\nLemur 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.\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.\n\n## Package advisory (CVE-2026-55165)\n\nAffected packages:\n\n- `lemur < 1.9.2`\n\nPatched in:\n\n- `lemur 1.9.2`\n\nSource: https://github.com/advisories/GHSA-r9gp-7f88-9r54","depth":"sunlit","depthScore":26,"depthScoreParts":{"impact":26.4,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}