Executive brief
Craft CMS is a web content management system that allows administrators to manage website content and user accounts. A vulnerability in versions before 5.10.11 allows an attacker to register a new account using the email address of a deactivated administrator and automatically inherit full administrator privileges. This requires the CMS to be configured to allow public registration without email verification—settings some deployments use—and could lead to complete unauthorized control over the website, all user accounts, and sensitive business data.
Technical details
The vulnerability is an improper privilege management flaw (CWE-269) in Craft CMS's user registration flow. The root cause is missing change-detection guards in the User::afterSave() method, which unconditionally writes the admin flag without authorization checks—unlike other security-sensitive user flags (active, pending, locked, suspended) that have protective guards. When public registration is enabled (allowPublicRegistration=true) and email verification is disabled (requireEmailVerification=false), an attacker can register using a deactivated admin's email address. The system reuses the inactive user record from the database, which still has admin=true set, and the missing guard allows the flag to persist into the newly activated account. No authentication is required beyond the ability to submit a registration form. Patches are available in version 5.10.11 and later.
Affected products
- Craft CMS 5.0.0-RC1 through 5.10.10
Timeline
- 2026-08-18: disclosed: GitHub Security Advisory GHSA-242m-9wq7-vhwq published
- 2026-09-02: advisory: CVE-2026-84795 published
- 2026-09-02: patched: Fix available in version 5.10.11