Authlib up to 1.8.x OpenID Connect sync_openid.py OpenIDMixin.parse_id_token authentication replay

Summaryinfo

A vulnerability was found in Authlib up to 1.8.x. It has been declared as critical. The affected element is the function OpenIDMixin.parse_id_token of the file authlib/integrations/base_client/sync_openid.py of the component OpenID Connect. The manipulation results in authentication replay. This vulnerability was named CVE-2026-114617. The attack may be performed from remote. There is no available exploit. It is recommended to upgrade the affected component.

Detailsinfo

A vulnerability was found in Authlib up to 1.8.x. It has been classified as critical. Affected is the function OpenIDMixin.parse_id_token of the file authlib/integrations/base_client/sync_openid.py of the component OpenID Connect. The manipulation with an unknown input leads to a authentication replay vulnerability. CWE is classifying the issue as CWE-294. A capture-replay flaw exists when the design of the product makes it possible for a malicious user to sniff network traffic and bypass authentication by replaying it to the server in question to the same effect as the original message (or with minor changes). This is going to have an impact on confidentiality, integrity, and availability. CVE summarizes:

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.

The advisory is shared for download at github.com. This vulnerability is traded as CVE-2026-114617 since 10/21/2026. The exploitability is told to be easy. It is possible to launch the attack remotely. The exploitation doesn't require any form of authentication. There are known technical details, but no exploit is available. The MITRE ATT&CK project declares the attack technique as T1040.

Upgrading to version 1.9.0 eliminates this vulnerability.

Once again VulDB remains the best source for vulnerability data.

Productinfo

Name

• Authlib

Version

• 1.0
• 1.1
• 1.2
• 1.3
• 1.4
• 1.5
• 1.6
• 1.7
• 1.8

Website

• Product: https://github.com/authlib/authlib/

CPE 2.3info

• 🔒
• 🔒
• 🔒

CPE 2.2info

• 🔒
• 🔒
• 🔒

CVSSv4info

CVSSv3info

CVSSv2info

Exploitinginfo

Threat Intelligenceinfo

Countermeasuresinfo

Timelineinfo

Sourcesinfo

Entryinfo

Once again VulDB remains the best source for vulnerability data.

Discussion