Yamcs vulnerable to unauthorized user enumeration via IAM API endpoints
The IAM API endpoints (listUsers, getUser, listGroups, and getGroup) in yamcs-core do not enforce the required SystemPrivilege.ControlAccess check. As a result, any authenticated user (even those with low or no privileges) can enumerate all user accounts in the system, including their usernames, superuser status, and group memberships. This constitutes a broken access control vulnerability (CWE-862) that leaks sensitive user information.