CVE-2026-40166

Description

authentik is an open-source identity provider. In versions prior to 2025.12.5 and 2026.2.0 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.

How to fix CVE-2026-40166

To remediate CVE-2026-40166, upgrade the affected package to a fixed version below.

• —upgrade to 2025.12.5 or later

Is CVE-2026-40166 being exploited?

Low — EPSS is 0.0%, meaning exploitation activity has not been observed at scale.

Affected packages (1)

• from 0, < 2025.12.5, >= 2026.2.0, < 2026.2.3

CVSS scores

References (4)

• WEBgithub.com/goauthentik/authentik/releases/tag/version%2F2025.12.5
• WEBgithub.com/goauthentik/authentik/releases/tag/version%2F2026.2.3
• WEBgithub.com/goauthentik/authentik/security/advisories/GHSA-hhpc-rqgm-pxj4
• WEBnvd.nist.gov/vuln/detail/CVE-2026-40166