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.
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Mon, 16 Mar 2026 20:15:00 +0000
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Mon, 16 Mar 2026 17:45:00 +0000
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| 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. | |
| Title | Authlib JWS JWK Header Injection: Signature Verification Bypass | |
| Weaknesses | CWE-347 | |
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cvssV3_1
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Status: PUBLISHED
Assigner: GitHub_M
Published: 2026-03-16T17:34:38.946Z
Updated: 2026-03-16T19:12:22.244Z
Reserved: 2026-02-25T03:24:57.792Z
Link: CVE-2026-27962
Updated: 2026-03-16T19:11:55.751Z
Status : Received
Published: 2026-03-16T18:16:07.383
Modified: 2026-03-16T18:16:07.383
Link: CVE-2026-27962
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