CVE-2026-56384

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

Published Jun 21, 2026 CVSS 4.0 · 5.3 Medium EPSS < 1% KEV · Not listed

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.

Analysis

Technical impact

Craft CMS contains a missing authorization flaw in the assets/preview-thumb endpoint. A Control Panel user that lacks permission to view a private asset can invoke the endpoint with any asset identifier and obtain preview HTML that includes a signed fallback preview link for that private asset. The vulnerability therefore allows an attacker to discover the details of a private asset and potentially access it through the generated preview link, exposing confidential content without proper authorization.

Affected Systems

The issue touches Craft CMS (CNU 4.0.0-RC1 through 4.17.7 and 5.0.0-RC1 through 5.9.13). These versions are affected; the fix is implemented in 4.17.8 and 5.9.14.

Risk and Exploitability

The flaw carries a CVSS score of 5.3, indicating moderate severity. The EPSS score is not available and the vulnerability is not listed as a known exploited vulnerability by CISA. Attackers need to be authenticated as a Control Panel user but do not require any special rights beyond a standard user account. Once authenticated, the attacker can request a preview for any private asset, gaining access to its signed preview link. The risk is moderate because the attack requires a compromised or legitimate account with insufficient asset‑view permissions, but the impact is significant as it permits disclosure of private asset content.

Affected Products

Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).

Vendor Product Default status Versions

craftcms

cms

unaffected

Version	Status	Constraints
`4.0.0-RC1`	affected	< 4.17.8
`4.17.8`	unaffected	—
`5.0.0-RC1`	affected	< 5.9.14
`5.9.14`	unaffected	—

No data.

Vendor Product Versions

Craftcms

Version	Status	Scheme	Platform
`[4.0.0-RC1,4.17.8)`	affected	semver	—
`4.17.8`	unaffected	semver	—
`[5.0.0-RC1,5.9.14)`	affected	semver	—
`5.9.14`	unaffected	semver	—

Remediation

No solution or workaround provided in the CVE record.

OpenCVE Recommended Actions

Upgrade Craft CMS to version 4.17.8 or later, or 5.9.14 or later to apply the vendor patch that resolves the missing authorization.
Review and tighten asset‑view permissions in the Control Panel to ensure only authorized users can view private assets, reducing the potential impact of any future authorization flaws.
If an immediate upgrade is not possible, block or restrict access to the assets/preview-thumb endpoint using web‑server or firewall rules so that only authenticated users with appropriate permissions can reach it.

Generated by OpenCVE AI on June 21, 2026 at 17:05 UTC.

Tracking

Advisories

Source	ID	Title
Github GHSA	GHSA-x76w-8c62-48mg	Craft CMS: Authenticated "assets/preview-thumb" discloses signed fallback transform preview link to CP users without asset-view permission

Metrics

Attack Vector Network

Attack Complexity Low

Privileges Required Low

Attack Requirements None

User Interaction None

Vulnerable System Confidentiality Impact Low

Vulnerable System Integrity Impact None

Vulnerable System Availability Impact None

Subsequent System Confidentiality Impact None

Subsequent System Integrity Impact None

Subsequent System Availability Impact None

Attack Vector Network

Attack Complexity Low

Privileges Required Low

Scope Unchanged

Confidentiality Impact Low

Integrity Impact None

Availability Impact None

User Interaction None

No CVSS v3.0

No CVSS v2

This CVE is not in the KEV list.

Exploit prediction score: < 1% (0.331% probability within 30 days)

Exploitation none

Automatable no

Technical Impact partial

References

Link	Providers
https://github.com/craftcms/cms/commit/d30df3112220db1ffd6726a3ed11857014c7fb27
https://github.com/craftcms/cms/security/advisories/GHSA-x76w-8c62-48mg
https://www.vulncheck.com/advisories/craft-cms-missing-authorization-in-assets-preview-thumb-endpoint

History

Jun 24, 2026 4:45 PM First appearance in the feed. Affected vendors updated View changes

Type	Values Removed	Values Added
First Time appeared		Craftcms Craftcms craftcms
Vendors & Products		Craftcms Craftcms craftcms

Jun 24, 2026 4:30 PM Scoring metrics updated View changes

Type	Values Removed	Values Added
Metrics		ssvc `{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}`

Jun 21, 2026 3:00 PM Description updated. Title updated. First appearance in the feed. Weaknesses updated. Affected versions updated. Affected vendors updated. Added references. Scoring metrics updated View changes

Type	Values Removed	Values Added
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.
Title		Craft CMS - Missing Authorization in assets/preview-thumb Endpoint
First Time appeared		Juzaweb Juzaweb cms
Weaknesses		CWE-862
CPEs		cpe:2.3:a:juzaweb:cms::::::::
Vendors & Products		Juzaweb Juzaweb cms
References		https://github.com/craftcms/cms/commit/d30df3112220db1ffd6726a3ed11857014c7fb27 https://github.com/craftcms/cms/security/advisories/GHSA-x76w-8c62-48mg https://www.vulncheck.com/advisories/craft-cms-missing-authorization-in-assets-preview-thumb-endpoint
Metrics		cvssV3_1 `{'score': 4.3, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N'}` cvssV4_0 `{'score': 5.3, 'vector': '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'}`