craftcms/cms security advisory

CVE-2026-33157: Craft CMS is Vulnerable to Authenticated Remote Code Execution via Malicious Attached Behavior

CVE-2026-33157 is a high-severity remote code execution vulnerability in the PHP package craftcms/cms (CVSS 7.2), published 24 March 2026. The advisory does not name a fixed version. Exploiting it needs an admin-level account.

high 7.2 published 2026-03-24 · updated 2026-06-17

Affected versions: >= 5.6.0, <= 5.9.12
Fixed in: not stated
Newest release: 5.12.0
Severity: High · CVSS 7.2
Type: Remote code execution
CWE-470
Exploited in the wild: Not on the CISA KEV list
checked 2026-11-04

Is your craftcms/cms version affected?

Run composer show craftcms/cms in your project, then enter the version. We check it against this and every other known craftcms/cms advisory.

Who can exploit CVE-2026-33157

Access: A high-privilege account in the app, such as an admin.

CVSS vector (scored by NVD): CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H

Your app is only exposed if it uses the affected part of craftcms/cms. The advisory below says which part that is. If you are not sure, upgrade anyway: it costs less than finding out.

How to fix CVE-2026-33157 in craftcms/cms

Find the installed version: composer show craftcms/cms. If you never required it yourself, composer why craftcms/cms shows which package pulls it in.
Update it: composer update craftcms/cms --with-all-dependencies.
If Composer will not go that high, your composer.json constraint is holding it back. Widen it (for example "craftcms/cms": "^5.12.0" if you can take that version), or upgrade the package that requires it.
Run composer audit. It reads the same advisory data and should no longer list CVE-2026-33157.
Commit composer.lock and deploy it. On the server, run composer install --no-dev from the lock file, not composer update.

If you cannot upgrade yet

General hardening for remote code execution issues while the upgrade waits. None of it replaces the fix.

Never pass user-controlled data to unserialize() or to template rendering, and restrict who can edit templates or settings.
Put a web application firewall in front of the app and watch for new PHP files or admin users.
If your app does not use the affected feature, note that in your audit, but still plan the upgrade.

The CVE-2026-33157 advisory

Craft CMS is a content management system (CMS). From version 5.6.0 to before version 5.9.13, a Remote Code Execution (RCE) vulnerability exists in Craft CMS, it can be exploited by any authenticated user with control panel access. This is a bypass of a previous fix. 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. This issue has been patched in version 5.9.13.

Description from the CVE record, published by GitHub (the CVE Numbering Authority), via the NVD entry for CVE-2026-33157. Advisory title: “Craft CMS is Vulnerable to Authenticated Remote Code Execution via Malicious Attached Behavior”.

References

GitHub advisory GHSA-2fph-6v5w-89hh github.com
Fix commit 97e90b4 github.com
Release 5.9.13 github.com

Other craftcms/cms advisories

critical Craft CMS: Passkey login accepts replayed WebAuthn assertions 2026-08-07
medium CVE-2026-72779: Craft CMS: Arbitrary file read via SplFileObject in non-sandboxed template contexts 2026-08-06
medium CVE-2026-72782: Craft CMS: Authenticated leak of secret environment variables 2026-08-06
medium CVE-2026-72785: Craft CMS: Authorization bypass: view-only Categories user can modify category structure via structures/move-element 2026-08-06
medium CVE-2026-14794: Craft CMS: Missing authorization check allows non-admin control panel users access to user registration metrics 2026-08-06
low CVE-2026-72783: Craft CMS: Incorrect path validation could potentially lead to path traversal 2026-08-06

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Where this data comes from

Affected and fixed versions: the Packagist security advisories API (GitHub Advisory Database and FriendsOfPHP), the same data composer audit uses. Synced 2026-11-03.
Description, score, weakness and references: NIST National Vulnerability Database (NVD), checked 2026-11-04. This product uses data from the NVD API but is not endorsed or certified by the NVD.
Exploited-in-the-wild status: the CISA Known Exploited Vulnerabilities catalog, checked 2026-11-04.
Compiled by Daniel Lasek at Laskyr from the sources above. The summary, “who can exploit it”, “how to fix it” and hardening sections are our plain-English reading of the record and are generated from it. The quoted description is the record's own text. Spot an error? Tell us.