CVE-2026-27962
critical · 9.1Authlib 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:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
Weaknesses
Affected products
| Vendor | Product | Affected versions |
|---|---|---|
| authlib | authlib | < 1.6.9 |
Check a specific version with /api/v1/cve/match.
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
Query this programmatically:
curl https://evil-db.io/api/v1/cve/CVE-2026-27962