CVE-2026-44011: Craft CMS: Potential authenticated Remote Code Execution via malicious attached Behavior

Craft CMS is a content management system (CMS). From 4.0.0 to before 4.17.12 and 5.9.18, Craft CMS which contains an input-handling flaw in a Yii object creation path that let any authenticated user inject malicious configuration and execute arbitrary commands on the server. The request-controlled condition field layouts data is converted into a live FieldLayout object without a Component::cleanseConfig() boundary. Because Craft configures models before parent::__construct(), attacker-controlled special config keys can take effect during object creation, and FieldLayout initialization then triggers a same-request event. This vulnerability is fixed in 4.17.12 and 5.9.18.