CVE-2026-56384 Craft CMS - Missing Authorization in assets/preview-thumb Endpoint
Craft CMS allows unauthorized users to view private asset previews due to missing permission checks in the preview-thumb endpoint.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-56384?
CVE-2026-56384 is a medium-severity missing authorization vulnerability in craftcms cms, published on 21 Jun 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Official description
Craft CMS contains a missing authorization vulnerability in the assets/preview-thumb endpoint. A Control Panel user without permission to view a target private asset can call the endpoint with an attacker-controlled assetId and receive preview HTML containing a signed fallback transform preview link for that private asset, because no asset-view permission check is performed before preview generation. This affects versions >= 4.0.0-RC1, <= 4.17.7 and >= 5.0.0-RC1, <= 5.9.13, and is fixed in 4.17.8 and 5.9.14.
Weakness: CWE-862
Which versions are affected by CVE-2026-56384?
4 open source packages ship an affected version, including craftcms/cms.
| Package | Affected | Fixed in |
|---|---|---|
craftcms/cms Packagist | From 4.0.0-RC1 | 4.17.8 |
craftcms/cms Packagist | From 4.0.0-RC1 | 4.17.8 |
craftcms/cms Packagist | From 5.0.0-RC1 | 5.9.14 |
craftcms/cms Packagist | From 5.0.0-RC1 | 5.9.14 |
How do I fix CVE-2026-56384?
Upgrade craftcms/cms to a fixed version for your release line: 4.17.8 or 5.9.14.
Upgrade, and check permissions on every request on the server, not only in the interface. More about Missing authorization.
Is CVE-2026-56384 being exploited?
There is no known exploitation of CVE-2026-56384 in the wild and no public exploit code.
Sources
Also known as GHSA-x76w-8c62-48mg.