CVE-2026-27962

CRITICAL EPSS 32.8%
Published Mar 16, 20263mo ago · Modified Jun 17, 20261w ago
9.1 CVSS 3.1
Critical
Find Similar
Published Mar 16, 2026 3mo ago
Last Modified Jun 17, 2026 1w ago

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.

CVSS Details

Base Score
9.1
Exploitability
3.9
Impact
5.2
Vector string
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
Attack Vector Network
Attack Complexity Low
Privileges Required None
User Interaction None
Scope Unchanged
Confidentiality High
Integrity High
Availability None

Threat Intelligence

EPSS Exploit Probability
32.8% percentile
Exploit & Patch Status
Public Exploit Known
Patch Available

Weaknesses 1

CWE-347

Affected Products 1

VendorProductVersionRange
authlibauthlib* <1.6.9

References 3

  • github.com https://github.com/authlib/authlib/commit/a5d4b2d4c9e46bfa11c82f85fdc2bcc0b50ae681
    Patch
  • github.com https://github.com/authlib/authlib/releases/tag/v1.6.9
    ProductRelease Notes
  • github.com https://github.com/authlib/authlib/security/advisories/GHSA-wvwj-cvrp-7pv5
    ExploitMitigationVendor Advisory

Remediation

  • github.com https://github.com/authlib/authlib/commit/a5d4b2d4c9e46bfa11c82f85fdc2bcc0b50ae681
    Patch