{"cve":"CVE-2026-55165","nvd":{"published":"2026-08-18T19:16:58.647","modified":"2026-09-08T21:02:26.047","status":"Deferred","description":"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.","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N","score":4.8},"cwes":["CWE-347"],"references":["https://github.com/Netflix/lemur/commit/89898e665beed044cf7bd5927dfaa484e55bf242","https://github.com/Netflix/lemur/releases/tag/v1.9.2","https://github.com/Netflix/lemur/security/advisories/GHSA-r9gp-7f88-9r54","https://github.com/Netflix/lemur/security/advisories/GHSA-r9gp-7f88-9r54"],"products":[],"source":"nvd","synced_at":"2026-10-19T22:49:10.689564601+00:00"},"epss":{"cve":"CVE-2026-55165","score":0.00154,"percentile":0.04499,"date":"2026-10-31"},"kev":null,"osv":[{"id":"GHSA-r9gp-7f88-9r54","url":"https://osv.dev/vulnerability/GHSA-r9gp-7f88-9r54","summary":" Lemur: JWT verifier honors attacker-supplied alg, enabling ATO","modified":"2026-07-13T16:42:40.412009090Z","packages":[{"ecosystem":"PyPI","name":"lemur","purl":"pkg:pypi/lemur","ranges":["<1.9.2"],"fixed":["1.9.2"]}]},{"id":"PYSEC-2026-2589","url":"https://osv.dev/vulnerability/PYSEC-2026-2589","summary":" Lemur: JWT verifier honors attacker-supplied alg, enabling ATO","modified":"2026-07-13T16:32:03.081746610Z","packages":[{"ecosystem":"PyPI","name":"lemur","purl":"pkg:pypi/lemur","ranges":["<1.9.2"],"fixed":["1.9.2"]}]}],"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."]}