ZDF
Sign inSign up

Vulnerabilities

Vulnerability · CVE-2026-27962

Authlib is a Python library which builds OAuth and OpenID Connect servers.

Published Mar 16, 2026 · catalog updated Sep 10, 2026 · Authlib is a Python

Check if you run it

No confirmed exploitation is on record for CVE-2026-27962. EPSS is 0.54%. Act only if a listed version of Authlib is a Python is installed.

Gaps on this record

  • The stored product name is a package slug. The name on this page is taken from the title (Authlib is a Python).
  • No version range is stored. A customer cannot check an installed version against this record.
  • No vendor fix or required action is stored. Compare the linked advisory before you change production.
Severity
Critical9.1
Known exploitation
Not in CISA/VulnCheck KEV
EPSS
0.54%
Remediation
Advisory link
Affected products
cpe authlib/authlib

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.

Are you affected?

Enter the version you run. The result uses only the ranges stored on this record.

The check returns affected, not affected, or incomplete. It does not guess a version that is missing from the record.

  • cpe authlib/authlibversion unspecified

How to fix CVE-2026-27962

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Should you patch?

No confirmed exploitation is on record for CVE-2026-27962. EPSS is 0.54%. Act only if a listed version of Authlib is a Python is installed.

Which versions are affected?

Affected version ranges are not on this record. Compare the installed version with the linked vendor advisory before you change production.

What should an analyst verify?

CWE-347: Improper Verification of Cryptographic Signature. EPSS 0.54%. There is no CISA KEV listing. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.

Code

The project this record applies to. Exploit listings stay in References.

Timeline

Detection, updates, and resolution for this record.

  1. Mar 16, 2026 · NIST NVD

    Detected

    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 atta

  2. Sep 10, 2026 · NIST NVD

    Updated

    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 atta

Sources

  • CVE.orgVulnerability recordCVE-2026-27962

    Official CVE identifier

    cve.org
  • FIRST EPSSExploitation probabilityCVE-2026-27962

    30-day exploitation probability 0.5%

    first.org
  • NIST NVDVulnerability recordCVE-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 pass signature verification. When key=None

    nvd.nist.gov

References

Freshness

Last verified in this catalog Oct 18, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.