CVE-2026-27962 — Security Box Score

CVE · referencelatest edition

Reference page — cumulative record through Wednesday, August 19, 2026 UTC. Reference pages update as the archive grows; only dated daily editions are immutable pages of record.

CVE-2026-27962CRITICAL

Authlib JWS JWK Header Injection: Signature Verification Bypass

  AV  AC  PR  UI  S  C  I  A   CVSS    EPSS   %ile   KEV
   N   L   N   N  U  H  H  N    9.1   .0055   43.5     —

AFFECTED
  Product  Versions   Fixed
  authlib  < 1.6.9 –  —

TIMELINE
  Feb 25  Reserved by GitHub_M
  Mar 16  Published (CNA: GitHub_M)
  Aug 17  EXPLOIT PUBLISHED — CVE-2026-27962 (authlib). Public exploit reference added.

CWE-347 · CNA: GitHub_M · CVSS v3.1 · 11 references · NVD status: Modified

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.

Lifecycle

Complete event history — 3 events, chronological
Date	Event	Detail
February 25, 2026	Reserved	Reserved by GitHub_M
March 16, 2026	Published	Published (CNA: GitHub_M)
August 17, 2026	EXPLOIT PUBLISHED	EXPLOIT PUBLISHED — CVE-2026-27962 (authlib). Public exploit reference added.

Affected

Affected products and packages — 1 row
Vendor	Product / Package	Ecosystem	Version introduced	Fixed
authlib	authlib	—	< 1.6.9	—

Weaknesses

CWE-347

References (11)

https://access.redhat.com/errata/RHSA-2026:19375 [vendor-advisory, x_refsource_REDHAT]
https://access.redhat.com/errata/RHSA-2026:24853 [vendor-advisory, x_refsource_REDHAT]
https://access.redhat.com/errata/RHSA-2026:48085 [vendor-advisory, x_refsource_REDHAT]
https://access.redhat.com/errata/RHSA-2026:5665 [vendor-advisory, x_refsource_REDHAT]
https://access.redhat.com/errata/RHSA-2026:7314 [vendor-advisory, x_refsource_REDHAT]
https://access.redhat.com/security/cve/CVE-2026-27962 [vdb-entry, x_refsource_REDHAT]
https://bugzilla.redhat.com/show_bug.cgi?id=2448164 [issue-tracking, x_refsource_REDHAT]
https://github.com/authlib/authlib/commit/a5d4b2d4c9e46bfa11c82f85fdc2bcc0b50ae681 [x_refsource_MISC]
https://github.com/authlib/authlib/releases/tag/v1.6.9 [x_refsource_MISC]
https://github.com/authlib/authlib/security/advisories/GHSA-wvwj-cvrp-7pv5 [x_refsource_CONFIRM]
https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-27962.json [x_sadp-csaf-vex]

Authoritative record: CVE-2026-27962 at cve.org

Vendors: authlib

Weaknesses: CWE-347

About this page

This is a reference page, not a dated page of record. It assembles the complete lifecycle of CVE-2026-27962 from the CVE Program record, NVD enrichment, the CISA KEV catalog, EPSS, and OSV advisories. The box score's numbers (CVSS, EPSS, KEV status) are current as of Wednesday, August 19, 2026 UTC and are re-derived as the archive grows; only dated daily editions are immutable pages of record. The authoritative source for this identifier is cve.org.