---
id: CVE-2026-114618
title: 'Authlib: Default JWT bearer grant accepts assertions for the wrong audience'
summary: >-
  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
  clai…
severity: medium
cvss: 6.8
cvssVector: 'CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:N'
cvssSource: cna
cwe:
  - CWE-287
  - CWE-1188
vendor: authlib
product: authlib
affected:
  - authlib < 1.9.0
published: '2026-10-22'
updated: '2026-10-22'
sourceUpdated: '2026-10-22T21:28:37.879Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-114618'
references:
  - url: 'https://github.com/authlib/authlib/security/advisories/GHSA-fch4-3c6x-j4gc'
    label: 'https://github.com/authlib/authlib/security/advisories/GHSA-fch4-3c6x-j4gc'
  - url: 'https://github.com/authlib/authlib/pull/945'
    label: 'https://github.com/authlib/authlib/pull/945'
  - url: >-
      https://github.com/authlib/authlib/commit/e3bd41cb29dcfee434453b135ffb487884baeedf
    label: >-
      https://github.com/authlib/authlib/commit/e3bd41cb29dcfee434453b135ffb487884baeedf
  - url: 'https://github.com/authlib/authlib/releases/tag/v1.9.0'
    label: 'https://github.com/authlib/authlib/releases/tag/v1.9.0'
tags:
  - cve.org
ingestedAt: '2026-10-22T22:00:50.448Z'
---

## Overview

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

- `authlib < 1.9.0`

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.