Executive brief
Craft CMS, a popular content management system, contains a security flaw that allows certain authorized users to view private files they should not have access to. Specifically, a user with access to the Control Panel can bypass permission restrictions to generate and view preview links for private assets. This could lead to the unauthorized disclosure of sensitive company images or documents stored within the system.
Technical details
A missing authorization vulnerability (CWE-862) exists in the 'assets/preview-thumb' endpoint of Craft CMS. The root cause is a failure to perform an asset-view permission check before generating preview HTML. An authenticated Control Panel user can provide an arbitrary 'assetId' to the endpoint to receive a signed fallback transform preview link for private assets they are not authorized to view. This results in unauthorized information disclosure of private assets. The issue is fixed in versions 4.17.8 and 5.9.14.
Affected products
- Craft CMS CMS >= 4.0.0-RC1, <= 4.17.7; >= 5.0.0-RC1, <= 5.9.13
Timeline
- 2026-06-02: advisory: Vendor advisory GHSA-x76w-8c62-48mg published
- 2026-06-21: disclosed: CVE-2026-56384 published to NVD