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Vulnerability · Published Oct 22, 2026 · Assigned by GitHub_M

CVE-2026-114618Authlib: Default JWT bearer grant accepts assertions for the wrong audience

Medium 6.8

In plain English

A medium-severity improper authentication in authlib from authlib. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.4% (higher than 29% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)6.8Medium
Exploit odds (30 days)0.4%top 71.1% of all CVEs
Exploited in the wildNo reportsCISA SSVC: poc
Attack toolingNoneno public tooling known

Official description

Authlib is a Python library which builds OAuth and OpenID Connect servers. Prior to 1.9.0, the default RFC 7523 JWTBearerGrant.get_audiences() returns an empty list, causing JWTBearerGrant.verify_claims() to require only that an aud claim exists without matching the current authorization server. An attacker holding a legitimate assertion for another service can present it to a server that shares the signing key and uses the default grant, obtaining an access token across a trust boundary. Implementations that override get_audiences() with the server's valid audience identifiers are not affected. This issue is fixed in version 1.9.0.

Affected packages & fixed versions

EcosystemPackageFixed inAdvisory
Debian:12python-authlibno fix listedDEBIAN-CVE-2026-114618
Debian:13python-authlibno fix listedDEBIAN-CVE-2026-114618
Debian:14python-authlib1.9.1-1DEBIAN-CVE-2026-114618
PyPIauthlib1.9.0GHSA-fch4-3c6x-j4gc
PyPIauthlib1.9.0PYSEC-2026-4358
Ubuntu:26.10python-authlibno fix listedUBUNTU-CVE-2026-114618

Affected products (as reported)

VendorProductVersions
authlib authlib < 1.9.0

Weakness: CWE-287, CWE-1188 · Vector: CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:N

References