{"schemaVersion":3,"id":"CVE-2026-27962","aliases":["GHSA-wvwj-cvrp-7pv5","PYSEC-2026-287","UBUNTU-CVE-2026-27962","DEBIAN-CVE-2026-27962"],"status":"published","duplicateOf":null,"title":null,"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. 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