Craft is a content management system (CMS). There is an authenticated admin RCE in Craft CMS 5.8.21 via Server-Side Template Injection using the create() Twig function combined with a Symfony Process gadget chain. The create() Twig function exposes Craft::createObject(), which allows instantiation of arbitrary PHP classes with constructor arguments. Combined with the bundled symfony/process dependency, this enables RCE. This bypasses the fix implemented for CVE-2025-57811 (patched in 5.8.7). This vulnerability is fixed in 5.9.0-beta.1 and 4.17.0-beta.1.

Affected: Packagist: craftcms/cms

There is an authenticated admin RCE in Craft CMS 5.8.21 via Server-Side Template Injection using the `create()` Twig function combined with a Symfony Process gadget chain.

This bypasses the fix implemented for CVE-2025-57811 (patched in 5.8.7).

## Required Permissions

- Administrator permissions or access to System Messages utility - `allowAdminChanges` enabled in production ([against our security recommendations](https://craftcms.com/knowledge-base/securing-craft#set-allowAdminChanges-to-false-in-production)) or access to System Messages utility

## Vulnerability Details The `create()` Twig function exposes `Craft::createObject()`, which allows instantiation of arbitrary PHP classes with constructor arguments. Combined with the bundled `symfony/process` dependency, this enables RCE.

## Attack Vector Admin panel → Settings → Entry Types → Title Format field

## Proof of Concept Payload

``` {% set p = create("Symfony\\Component\\Process\\Process", [["id"]]) %}{{ p.mustRun.getOutput }} ```

## Steps to Reproduce 1. Log in as admin 2. Navigate to Settings → Entry Types 3. Edit any entry type’s "Title Format" field 4. Insert the payload above 5. Create/edit an entry of that type 6. Command executes, output appears in entry title

## Impact - Authenticated Remote Code Execution - Runs as web server user (root in default Docker setup) - Full server compromise

## Root Cause Craft::createObject() allows the instantiation of any class, including `Symfony\Component\Process\Proc…