goauthentik up to 2025.12.4/2026.2.2 OAuth2 Access Token access_tokens client_id/client_secret information disclosure

Summaryinfo

A vulnerability was found in goauthentik authentik up to 2025.12.4/2026.2.2. It has been declared as problematic. Affected by this vulnerability is an unknown functionality of the file /api/v3/oauth2/access_tokens/ of the component OAuth2 Access Token Handler. Executing a manipulation of the argument client_id/client_secret can lead to information disclosure. This vulnerability is handled as CVE-2026-40166. The attack can be executed remotely. There is not any exploit available. It is recommended to upgrade the affected component.

Detailsinfo

A vulnerability classified as problematic was found in goauthentik authentik up to 2025.12.4/2026.2.2. This vulnerability affects some unknown processing of the file /api/v3/oauth2/access_tokens/ of the component OAuth2 Access Token Handler. The manipulation of the argument client_id/client_secret with an unknown input leads to a information disclosure vulnerability. The CWE definition for the vulnerability is CWE-200. The product exposes sensitive information to an actor that is not explicitly authorized to have access to that information. As an impact it is known to affect confidentiality. CVE summarizes:

authentik is an open-source identity provider. In versions prior to 2025.12.5 and 2026.2.0-rc1 through 2026.2.2, authenticated non-admin users with at least one OAuth2 access token can retrieve the client_secret of confidential OAuth2 providers they have previously authenticated against, exposing sensitive information to users without the correct permissions. This logic is GET /api/v3/oauth2/access_tokens/. The API response includes a nested provider object containing client_id and client_secret for providers configured with client_type: confidential, which should not be accessible to low-privilege users. This issue has been fixed in versions 2025.12.5 and 2026.2.3.

The advisory is available at github.com. This vulnerability was named CVE-2026-40166 since 04/09/2026. The exploitation appears to be easy. The attack can be initiated remotely. Technical details are known, but there is no available exploit. This vulnerability is assigned to T1592 by the MITRE ATT&CK project.

Upgrading to version 2025.12.5 or 2026.2.3 eliminates this vulnerability. The upgrade is hosted for download at github.com.

If you want to get best quality of vulnerability data, you may have to visit VulDB.

Productinfo

Vendor

• goauthentik

Name

• authentik

Version

• 2025.12.0
• 2025.12.1
• 2025.12.2
• 2025.12.3
• 2025.12.4
• 2026.2.0
• 2026.2.1
• 2026.2.2

Website

• Product: https://github.com/goauthentik/authentik/

CPE 2.3info

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CPE 2.2info

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