CVE-2026-27962
Critical · CVSS 9.1authlib — JWK Header Injection / JWT Signature Verification Bypass
- CVSS
- 9.1
- nvd
- EPSS
- 0.55%
- 43th pct
- KEV
- No
- Class
- oss containerizable
- CWE-347, CWE-347
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.
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Ranked PoCs (1) — best first
Heuristic ranking — not yet expert-vetted. Scored on structure + provenance, not execution.
- ★ 0
Recall-favoring discovery; ranking by the Stage-4 scorer (Adam's rubric). Scanner/aggregator repos are hidden.
Affected packages
| PyPI | authlib | 0 → 1.6.9 |
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
- https://access.redhat.com/errata/RHSA-2026:48085
- https://access.redhat.com/errata/RHSA-2026:5665
- https://access.redhat.com/errata/RHSA-2026:7314
- https://access.redhat.com/security/cve/CVE-2026-27962
- https://bugzilla.redhat.com/show_bug.cgi?id=2448164
- https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-27962.json
Status: enriched · ingested 2026-06-30T06:00:22.000Z · profiled 2026-07-01T00:30:14.000Z