CVE-2026-27962Authlib is a Python library which builds OAuth and OpenID Connect servers.
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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.
- CVSS
- 9.1 CRITICAL (v3.1, NVD)CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
- Weakness (CWE)
- CWE-347
- Known exploited
- Not in CISA's KEV catalog
- EPSS (exploitation in the next 30 days)
- Not loaded for this CVE
- Assigned by
- Not given
- NVD analysis
- Modified
- Record last updated
- Sep 10, 2026
- First seen by InfoSec Signals
- Oct 9, 2026
Affected products
authlib authlib authlib:authlib | before 1.6.9 | NVD |
References
- https://github.com/authlib/authlib/commit/a5d4b2d4c9e46bfa11c82f85fdc2bcc0b50ae681patch
- https://github.com/authlib/authlib/releases/tag/v1.6.9product, release-notes
- https://github.com/authlib/authlib/security/advisories/GHSA-wvwj-cvrp-7pv5exploit, mitigation, vendor-advisory
- 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
The CVE record on cve.org NVD's entry
The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.