Craft CMS is Vulnerable to Authenticated Remote Code Execution via Malicious Attached Behavior

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS 4.0

8.7 · CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N · score source

EPSS

• CVE-2026-33157: 1.11% estimated exploitation activity in the next 30 days; percentile 66.06 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary A Remote Code Execution (RCE) vulnerability exists in Craft CMS 5.x and 4.x that bypasses the security fixes for GHSA-7jx7-3846-m7w7 and GHSA-255j-qw47-wjh5. This vulnerability can be exploited by any authenticated user with control panel access. The existing patches add cleanseConfig() to assembleLayoutFromPost() and various FieldsController actions to strip Yii2 behavior/event injection keys (as and on prefixed keys). However, the fieldLayouts parameter in ElementIndexesController::actionFilterHud() is passed directly to FieldLayout::createFromConfig() without any sanitization, enabling the same behavior injection attack chain. Impact - Attack Type: Remote Code Execution (RCE) - Authentication Required: Authenticated user with control panel access (accessCp permission) Vulnerability Details Root Cause In ElementIndexesController::actionFilterHud() (line 493-494), the fieldLayouts body parameter is passed to FieldLayout::createFromConfig() without cleanseConfig(): Note the…

Published by the source

24 Mar 2026, 16:50 UTC

Last modified by the source

25 Mar 2026, 20:59 UTC

Source last checked

26 Oct 2026, 14:39 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-2fph-6v5w-89hh

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# Patch Next advisory brief: CVE-2026-33157

Advisory: Craft CMS is Vulnerable to Authenticated Remote Code Execution via Malicious Attached Behavior
IDs: CVE-2026-33157, GHSA-2fph-6v5w-89hh
Record: https://patchnext.com/advisories/cve-2026-33157 (revision 1, source checked 26 Oct 2026, 14:39 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 8.7)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: craftcms/cms 5.9.13. A vendor fix does not mean a deployment is fixed.

## Affected components
- Packagist craftcms/cms: affected >= 5.6.0, <= 5.9.12; fixed in 5.9.13

## Suggested inspection (read-only)
- Packagist craftcms/cms: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on craftcms/cms.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-2fph-6v5w-89hh (GitHub-reviewed advisory GHSA-2fph-6v5w-89hh lists affected ranges: Packagist craftcms/cms >=5.6.0 <=5.9.12)

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