Executive brief
The Auth0.js SDK, a library used to integrate authentication into web applications, contains a flaw in how it validates user identity. Under specific conditions, an attacker could provide a specially crafted token to bypass certain security checks and access sensitive user profile information. This could lead to unauthorized data exposure for applications that rely on Auth0 Actions for access control.
Technical details
An incorrect authorization vulnerability (CWE-863) exists in the Auth0.js SDK versions 8.11.0 through 9.32.0. The root cause is improper permission checking when processing a valid access token in conjunction with a specifically crafted, invalid ID token. This vulnerability is exploitable if the application's access control logic relies on rules defined in Auth0 Actions. A remote attacker with low privileges can exploit this over the network without user interaction to retrieve user profile data that should otherwise be protected. The issue is resolved in version 10.0.0.
Affected products
- Auth0 auth0-js 8.11.0 to 9.32.0
Timeline
- 2026-05-06: disclosed
- 2026-05-06: advisory
- 2026-05-06: patched: Fixed in version 10.0.0