Summary
Craft CMS: RCE via missing cleanseConfig in FieldsController::actionRenderCardPreview
The actionRenderCardPreview() method in FieldsController passes the fieldLayoutConfig POST parameter directly to Fields::createLayout() without calling Component::cleanseConfig(). This allows Yii2 event handler injection via on eventName keys in the config array, leading to arbitrary code execution.
This is the same vulnerability pattern that was fixed in GHSA-4484-8v2f-5748 (same file, _fldComponent method correctly uses cleanseConfig), GHSA-qx2q-q59v-wf3j (EntryTypesController), and GHSA-2fph-6v5w-89hh (ElementIndexesController).
PoC
As an admin user with a valid session:
POST /admin/actions/fields/render-card-preview HTTP/1.1
Content-Type: application/x-www-form-urlencoded
Cookie: CraftSessionId=<session>
fieldLayoutConfig[on+init]=phpinfo&CRAFT_CSRF_TOKEN=<token>
When the FieldLayout object is constructed, Yii2 processes the on init key as an event handler registration. During Component::init(), the init event is triggered, calling phpinfo(). The phpinfo output (which includes environment variables, potentially containing database credentials and CRAFT_SECURITY_KEY) will appear in the response.
Impact
An authenticated admin can achieve RCE through Yii2 event handler injection. While this requires admin access (same as GHSA-4484-8v2f-5748, which was rated moderate), it allows arbitrary PHP function execution and information disclosure via phpinfo.
Untrusted input is evaluated as executable code within the application's runtime environment. Typical impact: arbitrary code execution within the application's privilege context.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
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Frequently Asked Questions
- What is GHSA-86VW-X4WW-X467? GHSA-86VW-X4WW-X467 is a high-severity code injection vulnerability in craftcms/cms (composer), affecting versions >= 5.5.0, <= 5.9.13. It is fixed in 5.9.14. Untrusted input is evaluated as executable code within the application's runtime environment.
- Which versions of craftcms/cms are affected by GHSA-86VW-X4WW-X467? craftcms/cms (composer) versions >= 5.5.0, <= 5.9.13 is affected.
- Is there a fix for GHSA-86VW-X4WW-X467? Yes. GHSA-86VW-X4WW-X467 is fixed in 5.9.14. Upgrade to this version or later.
- Is GHSA-86VW-X4WW-X467 exploitable, and should I be worried? Whether GHSA-86VW-X4WW-X467 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether GHSA-86VW-X4WW-X467 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix GHSA-86VW-X4WW-X467? Upgrade
craftcms/cmsto 5.9.14 or later.