CVE-2026-56384

Craft CMS - Missing Authorization in assets/preview-thumb Endpoint

State: Published
Severity: 5.3 Medium
Published: Jun 21, 2026
Updated: Jun 24, 2026
Reserved: Jun 21, 2026

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.

Scores

CVSS	Score	Vector	Source
4.0	5.3 Medium	CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N	VulnCheck
3.1	4.3 Medium	CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N	VulnCheck

Weaknesses

CWE-862 Missing Authorization

Affected Products

Product	Versions
cmscraftcms	4.0.0-RC1 to before 4.17.8Affected 4.17.8Not affected 5.0.0-RC1 to before 5.9.14Affected 5.9.14Not affected

References

GHSA Advisory GHSA-x76w-8c62-48mgvendor-advisory
https://github.com/craftcms/cms/commit/d30df3112220db1ffd6726a3ed11857014c7fb27patch
VulnCheck Advisory: Craft CMS - Missing Authorization in assets/preview-thumb Endpointthird-party-advisory

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