GHSA-7jx7-3846-m7w7

## Relationship to Previously Patched Vulnerability This vulnerability is **in addition to** the RCE vulnerability patched in [GHSA-255j-qw47-wjh5](https://github.com/craftcms/cms/security/advisories/GHSA-255j-qw47-wjh5). That advisory addressed a similar RCE vulnerability that affected two specific routes: - `/index.php?p=admin%2Factions%2Ffields%2Fapply-layout-element-settings` - `/index.php?p=admin%2Factions%2Ffields%2Frender-card-preview` This one addresses some additional endpoints that were not covered in the https://github.com/craftcms/cms/security/advisories/GHSA-255j-qw47-wjh5. The patched vulnerability used a malicious `AttributeTypecastBehavior` with a wildcard event listener (`"on *": "self::beforeSave"`) and `__construct()` syntax to trigger RCE via the `typecastBeforeSave` callback. The fix was implemented in commits: - [6e608a1](https://github.com/craftcms/cms/commit/6e608a1a5bfb36943f94f584b7548ca542a86fef) - [27f5588](https://github.com/craftcms/cms/commit/27f55886098b56c00ddc53b69239c9c9192252c7) - [ec43c49](https://github.com/craftcms/cms/commit/ec43c497edde0b2bf2e39a119cded2e55f9fe593) This vulnerability follows the same attack pattern (behavior injection via `"as <behavior>"` syntax) but affects a **different code path** (`assembleLayoutFromPost()` in `Fields.php`) that was **not patched** in those commits. The attack vector uses `typecastAfterValidate` instead of `typecastBeforeSave` and does not require the wildcard event listener syntax, demonstrating that multiple entry points exist for this type of vulnerability. --- ## Executive Summary A Remote Code Execution (RCE) vulnerability exists in Craft CMS where the `assembleLayoutFromPost()` function in `src/services/Fields.php` fails to sanitize user-supplied configuration data before passing it to `Craft::createObject()`. This allows authenticated administrators to inject malicious Yii2 behavior configurations that execute arbitrary system commands on the server. This vulnerability represents an **unpatched variant** of the behavior injection vulnerability addressed in GHSA-255j-qw47-wjh5, affecting different endpoints through a separate code path. --- ## Vulnerability Details ### Attack Prerequisites - **Authentication:** Admin-level access required - **Network Access:** Access to admin panel (`/admin`) --- ### Location - **File:** `src/services/Fields.php` - **Function:** `assembleLayoutFromPost()` (lines 1125-1143) - **Root Cause:** Missing `cleanseConfig()` call on user-supplied `fieldLayout` POST parameter ### Vulnerable Code Path ```php // src/services/Fields.php:1125-1133 public function assembleLayoutFromPost(?string $namespace = null): FieldLayout { $paramPrefix = $namespace ? rtrim($namespace, '.') . '.' : ''; $request = Craft::$app->getRequest(); $config = JsonHelper::decode($request->getBodyParam("{$paramPrefix}fieldLayout")); // ... additional config values added ... $layout = $this->createLayout($config); // <-- No cleanseConfig() call! // ... } // src/services/Fields.php:1089-1093 public function createLayout(array $config): FieldLayout { $config['class'] = FieldLayout::class; return Craft::createObject($config); // <-- Untrusted data passed directly } ``` --- ## Attack Chain The exploitation leverages Yii2's object configuration system and behavior attachment mechanism: 1. **Behavior Injection:** Attacker includes `'as rce'` key in the `fieldLayout` JSON POST parameter 2. **Object Creation:** `Craft::createObject()` processes the config through Yii2's `BaseYii::configure()` 3. **Behavior Attachment:** Yii2's `Component::__set()` detects the `'as '` prefix and attaches the behavior 4. **RCE Trigger:** When `validate()` is called on the model, `EVENT_AFTER_VALIDATE` fires 5. **Command Execution:** `AttributeTypecastBehavior` calls the configured typecast function (`ConsoleProcessus::execute`) with the `uid` attribute value as the command ### RCE Gadget Chain ``` FieldLayout POST parameter → Craft::createObject() → Yii2 Component::__set() with 'as rce' key → AttributeTypecastBehavior attached → Model::validate() called → EVENT_AFTER_VALIDATE triggered → typecastAfterValidate → typecastAttributes() → call_user_func(['Psy\Readline\Hoa\ConsoleProcessus', 'execute'], $command) → Shell command execution ``` --- ## Affected Controllers The `assembleLayoutFromPost()` function is called by multiple admin controllers: | Controller | Action | Permission Required | |------------|--------|---------------------| | `TagsController` | `actionSaveTagGroup()` | Admin | | `CategoriesController` | `actionSaveGroup()` | Admin | | `EntryTypesController` | `actionSave()` | Admin | | `GlobalsController` | `actionSaveSet()` | Admin | | `VolumesController` | `actionSave()` | Admin | | `UsersController` | `actionSaveUserFieldLayout()` | Admin | | `AddressesController` | `actionSaveAddressFieldLayout()` | Admin | --- ## References - https://github.com/craftcms/cms/commit/395c64f0b80b507be1c862a2ec942eaacb353748 - [GHSA-255j-qw47-wjh5](https://github.com/craftcms/cms/security/advisories/GHSA-255j-qw47-wjh5) - Previously patched RCE vulnerability via behavior injection (affecting different endpoints) - [CVE-2024-4990](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2024-4990) - Related vulnerability that inspired the behavior injection attack pattern - [Yii2 GHSA-gcmh-9pjj-7fp4](https://github.com/yiisoft/yii2/security/advisories/GHSA-gcmh-9pjj-7fp4) - Original Yii framework report (framework team declined to fix at framework level) ---