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.
Affected products
authlib: authlib
References10
- github.com/authlib/authlib/security/advisories/GHSA-wvwj-cvrp-7… ExploitMitigationVendor Advisory
- github.com/authlib/authlib/commit/a5d4b2d4c9e46bfa11c82f85fdc2b… Patch
- github.com/authlib/authlib/releases/tag/v1.6.9 ProductRelease Notes
- access.redhat.com/errata/RHSA-2026:19375
- access.redhat.com/errata/RHSA-2026:24853
- access.redhat.com/errata/RHSA-2026:48085
- access.redhat.com/errata/RHSA-2026:5665
- access.redhat.com/errata/RHSA-2026:7314
- access.redhat.com/security/cve/CVE-2026-27962
- bugzilla.redhat.com/show_bug.cgi?id=2448164
Metrics
- CVSS 3.1
-
9.1
CRITICAL
Score source: CNA
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N - EPSS — exploit probability
- 1% percentile: 50 · as of 12 November 2026
- CWE
- CWE-347
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