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).
allowAdminChanges enabled in production (against our security recommendations) or access to System Messages utilityThe 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.
Admin panel → Settings → Entry Types → Title Format field
{% set p = create("Symfony\\Component\\Process\\Process", [["id"]])
%}{{ p.mustRun.getOutput }}
Craft::createObject() allows the instantiation of any class, including
Symfony\Component\Process\Process, which executes shell commands.
https://github.com/craftcms/cms/commit/e31e50849ad71638e11ea55fbd1ed90ae8f8f6e0
{
"github_reviewed": true,
"nvd_published_at": "2026-03-04T17:16:20Z",
"cwe_ids": [
"CWE-1336",
"CWE-22",
"CWE-94"
],
"github_reviewed_at": "2026-03-03T20:30:36Z",
"severity": "MODERATE"
}