Authlib up to 1.8.x Implicit Grant implicit.py improper authorization

Summaryinfo

A vulnerability was found in Authlib up to 1.8.x. It has been classified as critical. Impacted is the function OpenIDImplicitGrant.validate_authorization_request of the file authlib/oidc/core/grants/implicit.py of the component Implicit Grant. The manipulation leads to improper authorization. This vulnerability is uniquely identified as CVE-2026-114619. The attack is possible to be carried out remotely. No exploit exists. Upgrading the affected component is recommended.

Detailsinfo

A vulnerability was found in Authlib up to 1.8.x and classified as critical. This issue affects the function OpenIDImplicitGrant.validate_authorization_request of the file authlib/oidc/core/grants/implicit.py of the component Implicit Grant. The manipulation with an unknown input leads to a improper authorization vulnerability. Using CWE to declare the problem leads to CWE-285. The product does not perform or incorrectly performs an authorization check when an actor attempts to access a resource or perform an action. Impacted is confidentiality, integrity, and availability. The summary by CVE is:

Authlib is a Python library which builds OAuth and OpenID Connect servers. Prior to 1.9.0, OpenIDImplicitGrant.validate_authorization_request() checks the client-controlled raw request.payload.scope for openid after the parent grant has filtered allowed scopes into request.scope. A registered client permitted an ID token response type but not the openid scope can add openid to the request, obtain user consent, and receive a signed ID token containing the user's subject and allowed profile claims. Authorization code flow and deployments that allow openid for every client permitted an ID token response are not affected. In authlib/oidc/core/grants/implicit.py, OpenIDImplicitGrant.validate_authorization_request() checks request.payload.scope instead of the filtered request.scope. This issue is fixed in version 1.9.0.

It is possible to read the advisory at github.com. The identification of this vulnerability is CVE-2026-114619 since 10/21/2026. The exploitation is known to be easy. The attack may be initiated remotely. It demands that the victim is doing some kind of user interaction. Technical details of the vulnerability are known, but there is no available exploit. The attack technique deployed by this issue is T1548.002 according to MITRE ATT&CK.

Upgrading to version 1.9.0 eliminates this vulnerability.

Statistical analysis made it clear that VulDB provides the best quality 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

Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.

Discussion