CVE-2026-114617 Authlib: ID token can disable its own nonce validation via the nonce_supported claim

What is CVE-2026-114617?

CVE-2026-114617 is a medium-severity vulnerability in authlib, published on 22 Oct 2026.

Official description

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.

Weakness: CWE-807, CWE-294

Which versions are affected by CVE-2026-114617?

2 open source packages ship an affected version, including authlib. It affects 1 product.

Products include Authlib Authlib.

How do I fix CVE-2026-114617?

Upgrade authlib to 1.9.0 or later.

Is CVE-2026-114617 being exploited?

There is no known exploitation of CVE-2026-114617 in the wild and no public exploit code.

Other vulnerabilities in authlib

• CVE-2026-27962 Authlib JWS JWK Header Injection: Signature Verification Bypass Critical 9.1
• CVE-2026-28490 Authlib Vulnerable to JWE RSA1_5 Bleichenbacher Padding Oracle High 8.3
• CVE-2026-28498 Authlib: Fail-Open Cryptographic Verification in OIDC Hash Binding High 8.2
• CVE-2026-28802 Authlib: Setting `alg: none` and a blank signature appears to bypass signature verification High 7.7
• CVE-2025-61920 Authlib is vulnerable to Denial of Service via Oversized JOSE Segments High 7.5

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as DEBIAN-CVE-2026-114617, ECHO-1fc4-2a5e-a20a, GHSA-c5mf-xmp2-59rc, MINI-5pfm-5j5p-mc5r, UBUNTU-CVE-2026-114617.