Lewis Philbey

**Name of the Vulnerable Software and Affected Versions** MISP versions prior to 2.4.80 **Description** The issue arises when MISP is configured with X.509 certificate authentication in conjunction with an external user management ReST API. If this API returns an empty value for an external user providing X.509 certificate authentication, an unauthenticated user can gain access as an arbitrary user. **Recommendations** For versions prior to 2.4.80, update to version 2.4.80 or later to resolve the issue. As a temporary workaround, consider disabling the X.509 certificate authentication feature until the update is applied. Restrict access to the external user management ReST API to minimize the risk of exploitation. Avoid using empty values in the API responses for X.509 certificate authentication until the issue is resolved.