Description

Unauthenticated Craft CMS users can trigger a database backup Unauthenticated users can trigger database backup operations the updater/backup action, potentially leading to resource exhaustion or information disclosure.

Users should update to the patched versions (5.8.21 and 4.16.17) to mitigate the issue.

Craft 3 users should update to the latest Craft 4 and 5 releases, which include the fixes.

References:

https://github.com/craftcms/cms/commit/f83d4e0c6b906743206b4747db4abf8164b8da39

https://github.com/craftcms/cms/blob/5.x/CHANGELOG.md#5821---2025-12-04

Affected Endpoints

POST /admin/actions/updater/backup (unauthenticated)

Vulnerability Details

Root Cause

All updater/* actions are explicitly configured with anonymous access:

// BaseUpdaterController.php  
protected array|bool|int $allowAnonymous = self::ALLOW_ANONYMOUS_LIVE | self::ALLOW_ANONYMOUS_OFFLINE;

Attack Vector

Send unauthenticated POST request to /admin/actions/updater/backup

Database backup executes with configured backupCommand

Mitigation

Aliases

References