GHSA-265m-7826-wjqm Craft CMS: Authenticated RCE via `condition.config` JSON cleanse bypass

• Packagist craftcms/cms: >= 5.0.0-RC1, < 5.10.6 → fixed in 5.10.6 • Packagist craftcms/cms: >= 4.0.0-RC1, < 4.18.2 → fixed in 4.18.2

Craft CMS has an authenticated remote code execution issue in the control panel element-search condition handling. Craft cleans the outer request-controlled condition array with `Component::cleanseConfig()`, but `Conditions::createCondition()` later decodes and merges the JSON string in `condition.config` without re-running `cleanseConfig()` on the decoded/merged configuration. Because `condition.config` is a JSON string during the first cleanse, Yii special config keys such as `as` ... and `on` ... can be hidden inside it. After JSON decoding, those keys reach FieldLayout object creation and are interpreted by Yii as behavior/event configuration. The RCE is semi-blind: the trigger endpoint returns a normal JSON response, and the command output is verified via a server-side file-write side effect retrieved in a subsequent request. Preconditions • The attacker needs an authenticated Craft control panel session. • A valid CSRF token is required. Impact An authenticated control panel user can inject Yii behavior/event configuration after Craft’s intended config cleanse boundary. In the confirmed local lab, this led to command execution as the PHP/web user. Potential attacker impact: • Execute operating system commands as the PHP/web user. • Read Craft secrets, environment variables, and application configuration. • Access database credentials and stored site content. • Modify site content, users, and application state. • Pivot to internal services reachable from the Craft host or container. • Cause denial of service or establish persistence depending on deployment permissions.