CriticalFix available
python-authlib — security advisory
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.
- Products
- python-authlib
- Affected versions
- 0.15.4-1, 0.15.5-1, 0.15.5-1ubuntu0.1~esm1, 1.2.1-1, 1.3.0-1, 1.3.0-1ubuntu0.1~esm1, 1.5.1-1, 1.5.2-1, 1.6.0-1, 1.6.5-1, 1.6.6-1, 1.6.7-1, 1.7.2-1, 1.7.2-2
- Fixed versions
- 0.15.5-1ubuntu0.1~esm2, 1.3.0-1ubuntu0.1~esm2, 1.6.7-1ubuntu0.1~esm1
- CVEs
- CVE-2026-27962
- Confirmed fixed CVEs
- Not specified
- Updated in this feed
- 31 Oct 2026, 02:58 UTC · Revision 1
Source evidence
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.
osv:UBUNTU-CVE-2026-27962
python-authlib
Fixed versions: 0.15.5-1ubuntu0.1~esm2
python-authlib
Fixed versions: 1.3.0-1ubuntu0.1~esm2
python-authlib
Fixed versions: Not specified
python-authlib
Fixed versions: Not specified
python-authlib
Fixed versions: 1.6.7-1ubuntu0.1~esm1
Complete source record
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"modified": "2026-10-17T12:59:56.992027275Z",
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