CVE-2026-109308
Received Received - Intake

Behavior Injection in Craft CMS

Publication date: 2026-10-12

Last updated on: 2026-10-12

Assigner: VulnCheck

Description
Craft CMS 4.0.0 before 4.18.7 and 5.0.0 before 5.10.14 passes the raw 'updates' request parameter in AppController::actionCacheUpdates to UpdatesModel without Component::cleanseConfig(), allowing behavior and event-handler injection. Authenticated control panel users with the performUpdates permission or Updates-utility access can supply 'as' or 'on' keys, such as an AttributeTypecastBehavior gadget, to execute arbitrary code.

CVSS Scores

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Meta Information

Published
2026-10-12
Last Modified
2026-10-12
Generated
2026-10-12
AI Q&A
2026-10-12
EPSS Evaluated
N/A
NVD
CVE-2026-109308
EUVD
EUVD-2026-97610

Affected Vendors & Products

Showing 2 associated CPEs
Vendor Product Version / Range
craftcms cms 4.0.0
craftcms cms 5.0.0

Helpful Resources

Exploitability

CWE
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KEV
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CWE ID Description
CWE-94 The product constructs all or part of a code segment using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the syntax or behavior of the intended code segment.

Attack-Flow Graph

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Executive Summary

CVE-2026-109308 is a Remote Code Execution (RCE) vulnerability in Craft CMS versions 4.0.0 through 4.18.6 and 5.0.0 through 5.10.13. The issue occurs because the application passes the raw 'updates' request parameter to UpdatesModel without sanitization. Authenticated control panel users with limited permissions can inject malicious 'as' or 'on' keys to trigger arbitrary code execution via behavior or event-handler injection.

Detection Guidance

Check Craft CMS version installed on your system. Vulnerable versions are 4.0.0 to 4.18.6 and 5.0.0 to 5.10.13. Run: composer show craftcms/cms or check the version in the Craft CMS admin panel. Also review logs for suspicious activity from control panel users with performUpdates permission.

Impact Analysis

An attacker with control panel access and performUpdates permission or Updates utility access could execute arbitrary code on the server. This could lead to full system compromise, data theft, or unauthorized modifications. The high CVSS score (8.7/8.8) indicates significant risk due to the potential for complete system takeover.

Compliance Impact

This vulnerability could lead to unauthorized data access or modification, violating GDPR's integrity and confidentiality principles or HIPAA's security requirements. Organizations using vulnerable Craft CMS versions may face compliance violations, legal penalties, and reputational damage if exploited.

Mitigation Strategies

Upgrade Craft CMS to version 4.18.7 or later for 4.x or 5.10.14 or later for 5.x immediately. Remove or restrict access to the Updates utility for non-admin users. Disable the performUpdates permission for users who do not require it.

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