---
id: CVE-2026-114617
title: >-
  Authlib: ID token can disable its own nonce validation via the nonce_supported
  claim
summary: >-
  Authlib is a Python library which builds OAuth and OpenID Connect servers.
  Prior to 1.9.0, OpenIDMixin.parse_id_token() reads the nonce_supported
  decision from the untrusted ID token being validated and sets the expected
  nonce to null wh…
severity: medium
cvss: 4.2
cvssVector: 'CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:L/I:L/A:N'
cvssSource: cna
cwe:
  - CWE-294
  - CWE-807
vendor: authlib
product: authlib
affected:
  - authlib < 1.9.0
published: '2026-10-22'
updated: '2026-10-22'
sourceUpdated: '2026-10-22T21:25:31.732Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-114617'
references:
  - url: 'https://github.com/authlib/authlib/security/advisories/GHSA-c5mf-xmp2-59rc'
    label: 'https://github.com/authlib/authlib/security/advisories/GHSA-c5mf-xmp2-59rc'
  - url: 'https://github.com/authlib/authlib/pull/949'
    label: 'https://github.com/authlib/authlib/pull/949'
  - url: >-
      https://github.com/authlib/authlib/commit/6563f6f7a8c2f71d2f85ee7511d72a4fbae3acc0
    label: >-
      https://github.com/authlib/authlib/commit/6563f6f7a8c2f71d2f85ee7511d72a4fbae3acc0
  - 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: '2026-10-22T22:00:50.446Z'
---

## Overview

Authlib is a Python library which builds OAuth and OpenID Connect servers. Prior to 1.9.0, OpenIDMixin.parse_id_token() reads the nonce_supported decision from the untrusted ID token being validated and sets the expected nonce to null when that claim is the JSON boolean false. In implicit and hybrid relying parties, or applications that directly accept externally supplied ID tokens, an attacker with a captured validly signed token can bypass the nonce-to-session binding and replay the victim's token into an attacker-controlled session. Plain authorization code flow is not affected, and the token must still pass signature, issuer, and audience validation. OpenIDMixin.parse_id_token() trusts nonce_supported in both authlib/integrations/base_client/sync_openid.py and authlib/integrations/base_client/async_openid.py to disable the expected nonce. 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.