Craft CMS Vulnerable to potential authenticated Remote Code Execution via malicious attached Behavior

Exploitation

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

CVSS 4.0

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

EPSS

• CVE-2026-25498: 1.12% estimated exploitation activity in the next 30 days; percentile 66.13 (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.

Relationship to Previously Patched Vulnerability This vulnerability is in addition to the RCE vulnerability patched in GHSA-255j-qw47-wjh5. That advisory addressed a similar RCE vulnerability that affected two specific routes: - /index.php?p=admin%2Factions%2Ffields%2Fapply-layout-element-settings - /index.php?p=admin%2Factions%2Ffields%2Frender-card-preview This one addresses some additional endpoints that were not covered in the https://github.com/craftcms/cms/security/advisories/GHSA-255j-qw47-wjh5. The patched vulnerability used a malicious AttributeTypecastBehavior with a wildcard event listener ("on ": "self::beforeSave") and construct() syntax to trigger RCE via the typecastBeforeSave callback. The fix was implemented in commits: - 6e608a1 - 27f5588 - ec43c49 This vulnerability follows the same attack pattern (behavior injection via "as <behavior" syntax) but affects a different code path (assembleLayoutFromPost() in Fields.php) that was not patched in those commits. The…

Published by the source

9 Feb 2026, 20:36 UTC

Last modified by the source

9 Feb 2026, 22:39 UTC

Source last checked

26 Oct 2026, 14:38 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-7jx7-3846-m7w7

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# Patch Next advisory brief: CVE-2026-25498

Advisory: Craft CMS Vulnerable to potential authenticated Remote Code Execution via malicious attached Behavior
IDs: CVE-2026-25498, GHSA-7jx7-3846-m7w7
Record: https://patchnext.com/advisories/cve-2026-25498 (revision 1, source checked 26 Oct 2026, 14:38 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 8.6)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: craftcms/cms 5.8.22, 4.16.18. A vendor fix does not mean a deployment is fixed.

## Affected components
- Packagist craftcms/cms: affected >= 5.0.0-RC1, <= 5.8.21; >= 4.0.0-RC1, <= 4.16.17; fixed in 5.8.22, 4.16.18

## 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-7jx7-3846-m7w7 (GitHub-reviewed advisory GHSA-7jx7-3846-m7w7 lists affected ranges: Packagist craftcms/cms >=5.0.0-RC1 =4.0.0-RC1 <=4.16.17)

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