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4.2
CVE-2026-114617: Authlib before 1.9 allows token to skip nonce check
CVE-2026-114617 · published 13 days ago
Summary
The Authlib library used to create login services could be tricked into ignoring a security check called the nonce when a specially crafted ID token says it is not needed. This lets an attacker reuse a captured token and log in as the victim in certain login flows. Upgrade Authlib to version 1.9.0 or later to restore the nonce validation.
What to do
- Update authlib to version 1.9.0.
- Update debian python-authlib to version 1.9.1-1.
- Update authlib authlib to version 1.9.0 or later.
Affected software
| Ecosystem | Vendor | Product | Affected versions |
|---|---|---|---|
| – | authlib | authlib | < 1.9.0 |
| Debian:12 | debian | python-authlib | All versions |
| pip | – | authlib |
<= 1.8.0 Fix: upgrade to 1.9.0
|
| PyPI | – | authlib |
< 1.9.0 Fix: upgrade to 1.9.0
|
| Debian:14 | debian | python-authlib |
< 1.9.1-1 Fix: upgrade to 1.9.1-1
|
Original advisory text
Authlib: ID token can disable its own nonce validation via the nonce_supported claim
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.
References
- https://github.com/authlib/authlib/commit/6563f6f7a8c2f71d2f85ee7511d72a4fbae3ac... Patch
- https://github.com/authlib/authlib/pull/949 Patch
- https://github.com/authlib/authlib/releases/tag/v1.9.0 URL
- https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/114xxx/CVE-2026-1146... Vendor Advisory
- https://nvd.nist.gov/vuln/detail/CVE-2026-114617 Vendor Advisory
- https://security-tracker.debian.org/tracker/CVE-2026-114617 Vendor Advisory
- https://github.com/advisories/GHSA-c5mf-xmp2-59rc
- https://github.com/authlib/authlib/security/advisories/GHSA-c5mf-xmp2-59rc Vendor Advisory
- https://github.com/authlib/authlib Product
Internet-facing
60 days
Internal
At next upgrade
- Not known to be exploited
- Needs hands-on effort to exploit
- Gives an attacker partial control
Type
CWE-294Authentication Bypass by Capture-replay
CWE-807Reliance on Untrusted Inputs in a Security Decision
Timeline
Published22 Oct 2026
Updated3 Nov 2026
First seen22 Oct 2026
Sources
CVE-2026-114617 · NVD
CVE-2026-114617 · MITRE
CVE-2026-114617 · OSV
GHSA-c5mf-xmp2-59rc · GHSA
DEBIAN-CVE-2026-114617 · OSV
GHSA-c5mf-xmp2-59rc · OSV
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