{"cve":"CVE-2026-27962","nvd":{"published":"2026-03-16T18:16:07.383","modified":"2026-09-10T13:18:01.463","status":"Modified","description":"Authlib is a Python library which builds OAuth and OpenID Connect servers. Prior to version 1.6.9, a JWK Header Injection vulnerability in authlib's JWS implementation allows an unauthenticated attacker to forge arbitrary JWT tokens that pass signature verification. When key=None is passed to any JWS deserialization function, the library extracts and uses the cryptographic key embedded in the attacker-controlled JWT jwk header field. An attacker can sign a token with their own private key, embed the matching public key in the header, and have the server accept the forged token as cryptographically valid — bypassing authentication and authorization entirely. This issue has been patched in version 1.6.9.","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:N","score":9.1},"cwes":["CWE-347"],"references":["https://github.com/authlib/authlib/commit/a5d4b2d4c9e46bfa11c82f85fdc2bcc0b50ae681","https://github.com/authlib/authlib/releases/tag/v1.6.9","https://github.com/authlib/authlib/security/advisories/GHSA-wvwj-cvrp-7pv5","https://access.redhat.com/errata/RHSA-2026:19375","https://access.redhat.com/errata/RHSA-2026:24853"],"products":["authlib:authlib"],"source":"nvd","synced_at":"2026-10-19T22:26:19.218427112+00:00"},"epss":{"cve":"CVE-2026-27962","score":0.00558,"percentile":0.46497,"date":"2026-10-31"},"kev":null,"osv":[{"id":"GHSA-wvwj-cvrp-7pv5","url":"https://osv.dev/vulnerability/GHSA-wvwj-cvrp-7pv5","summary":"Authlib JWS JWK Header Injection: Signature Verification Bypass","modified":"2026-10-27T15:30:03.187299955Z","packages":[{"ecosystem":"PyPI","name":"authlib","purl":"pkg:pypi/authlib","ranges":["<1.6.9"],"fixed":["1.6.9"]}]},{"id":"PYSEC-2026-287","url":"https://osv.dev/vulnerability/PYSEC-2026-287","summary":"Authlib JWS JWK Header Injection: Signature Verification Bypass","modified":"2026-07-13T16:15:15.641042659Z","packages":[{"ecosystem":"PyPI","name":"authlib","purl":"pkg:pypi/authlib","ranges":["<1.6.9"],"fixed":["1.6.9"]}]}],"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."]}