CVE-2026-40166 authentik: Non-admin user can retrieve confidential OAuth client_secret via /api/v3/oauth2/access_tokens/
Authenticated non-admin users can retrieve confidential OAuth client secrets via the access tokens API, exposing sensitive credentials.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-40166?
CVE-2026-40166 is a high-severity vulnerability in goauthentik authentik, published on 22 May 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Official description
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.
Which versions are affected by CVE-2026-40166?
1 open source package ship an affected version, including authentik.
| Package | Affected | Fixed in |
|---|---|---|
authentik Bitnami | All versions | 2025.12.5, 2026.2.3 |
How do I fix CVE-2026-40166?
Upgrade authentik to a fixed version for your release line: 2025.12.5 or 2026.2.3.
Is CVE-2026-40166 being exploited?
There is no known exploitation of CVE-2026-40166 in the wild and no public exploit code.
Sources
Also known as BIT-authentik-2026-40166, GHSA-hhpc-rqgm-pxj4.