{"id":"GHSA-7pfv-hr63-h7cw","aliases":["CVE-2026-30927"],"title":"Admidio: Event participation IDOR - non-leaders can register other users for events via user_uuid parameter","description":"## Vulnerability\n\nIn `modules/events/events_function.php`, the event participation logic allows any user who can participate in an event to register OTHER users by manipulating the `user_uuid` GET parameter.\n\nLine 47: `$getUserUuid = admFuncVariableIsValid($_GET, 'user_uuid', 'uuid', ...)`\nLine 424: `if ($event->possibleToParticipate() || $participants->isLeader($gCurrentUserId))`\n\nThe condition uses `||` (OR), meaning if `possibleToParticipate()` returns true (event is open for participation), ANY user - not just leaders - can specify a different `user_uuid` and register/cancel participation for that user.\n\nThe code then operates on `$user->getValue('usr_id')` (the target user from user_uuid) rather than the current user.\n\n## Impact\n- Register unwilling users for events (potential harassment/spam)\n- Cancel other users' event participation\n- Manipulate event participant counts and comments\n- If events have participation limits, fill slots with unwanted registrations\n\n## Fix\nFor non-leader users, force `user_uuid` to the current user:\n```php\nif (!$participants->isLeader($gCurrentUserId)) {\n    $getUserUuid = $gCurrentUser->getValue('usr_uuid');\n}\n```","severity":"low","score":0,"published":"2026-03-09T19:45:20.000Z","modified":"2026-03-10T18:48:30.504Z","withdrawn":false,"knownExploited":false,"affected":[{"ecosystem":"Packagist","name":"admidio/admidio","ranges":[{"events":[{"introduced":"0"},{"fixed":"5.0.6"}],"type":"ECOSYSTEM"}],"versions":["4.1.0","4.1.3","v4.2-Beta.1","v4.2-Beta.2","v4.2-Beta.3","v4.2.0","v4.2.1","v4.2.10","v4.2.11","v4.2.12","v4.2.13","v4.2.14","v4.2.2","v4.2.3","v4.2.4","v4.2.5","v4.2.6","v4.2.7","v4.2.8","v4.2.9","v4.3-Beta.1","v4.3-Beta.3","v4.3-Beta.4","v4.3-Beta.5","v4.3.0","v4.3.1","v4.3.10","v4.3.11","v4.3.12","v4.3.13","v4.3.14","v4.3.15","v4.3.16","v4.3.17","v4.3.2","v4.3.3","v4.3.4","v4.3.5","v4.3.6","v4.3.7","v4.3.8","v4.3.9","v5.0-Beta.1","v5.0-Beta.2","v5.0-Beta.3","v5.0.0","v5.0.1","v5.0.2","v5.0.3","v5.0.4","v5.0.5"],"fixed":["5.0.6"]}],"references":["https://github.com/Admidio/admidio/security/advisories/GHSA-7pfv-hr63-h7cw","https://nvd.nist.gov/vuln/detail/CVE-2026-30927","https://github.com/Admidio/admidio/issues/1985","https://github.com/Admidio/admidio/commit/e47f70cc3cbcdb39635fdbaaef02d19f604b8c3e","https://github.com/Admidio/admidio"],"sources":[{"name":"OSV","id":"GHSA-7pfv-hr63-h7cw","modified":"2026-03-10T18:48:30.504905Z","url":"https://osv.dev/vulnerability/GHSA-7pfv-hr63-h7cw"}],"assessments":[{"source":"OSV","vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:N","score":0},{"source":"OSV","vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:L/VA:L/SC:N/SI:N/SA:N","score":5.3}]}