What is CVE-2026-27962?

CVE-2026-27962 is a critical-severity vulnerability in Authlib, classified under Improper Verification of Cryptographic Signature. CVSS score: 9.1/10. Published 2026-03-16.

How severe is CVE-2026-27962?

Critical severity. CVSS v3 base score is 9.1 out of 10.

Vulnerability in Authlib

CVE-2026-27962

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 p…

EPSS: 0.001 (23.9th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 9.1 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N.

Affected products

Authlib — versions < 1.6.9

Weakness classification (CWE)

CWE-347 — Improper Verification of Cryptographic Signature

References

https://github.com/authlib/authlib/security/advisories/GHSA-wvwj-cvrp-7pv5 (x_refsource_CONFIRM)
https://github.com/authlib/authlib/commit/a5d4b2d4c9e46bfa11c82f85fdc2bcc0b50ae681 (x_refsource_MISC)
https://github.com/authlib/authlib/releases/tag/v1.6.9 (x_refsource_MISC)

Frequently asked questions

What is CVE-2026-27962?: CVE-2026-27962 is a critical-severity vulnerability in Authlib, classified under Improper Verification of Cryptographic Signature. CVSS score: 9.1/10. Published 2026-03-16.
How severe is CVE-2026-27962?: Critical severity. CVSS v3 base score is 9.1 out of 10.