CVE-2026-27962
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.
Predictions
Heuristic predictions, AS-IS, for prioritization only.
Mitigations
Vendor advisory: debian — https://security-tracker.debian.org/tracker/CVE-2026-27962
Vendor advisory: suse — https://www.suse.com/security/cve/CVE-2026-27962.html
OS impact
| OS | Version | Status | Fixed in |
|---|---|---|---|
| sles | affected | | |
| debian | bookworm | affected | |
| debian | bullseye | fixed | 0.15.4-1+deb11u2 |
| debian | forky | fixed | 1.6.9-1 |
| debian | sid | fixed | 1.6.9-1 |
| debian | trixie | affected | |
Package impact
| Ecosystem | Package | Vulnerable | Fixed |
|---|---|---|---|
| PyPI | authlib | <1.6.9 | 1.6.9 |
References
- https://github.com/authlib/authlib/security/advisories/GHSA-wvwj-cvrp-7pv5
- https://nvd.nist.gov/vuln/detail/CVE-2026-27962
- https://github.com/authlib/authlib/commit/a5d4b2d4c9e46bfa11c82f85fdc2bcc0b50ae681
- https://github.com/authlib/authlib
- https://github.com/authlib/authlib/releases/tag/v1.6.9
- https://www.suse.com/security/cve/CVE-2026-27962.html
- https://security-tracker.debian.org/tracker/CVE-2026-27962
Verify integrity in audit chain (admin only). AS-IS.