CVE-2026-56385: Authorization Bypass Through User-Controlled Key in craftcms cms
### Summary An authenticated low-privileged user can call `assets/preview-file` for an asset they are not authorized to view and still receive preview response data (`previewHtml`) for that private asset. The returned preview HTML included a private preview image route containing the target private `assetId`, even though `canView` was `false` for the attacker account. ### Details 1. `assets/preview-file` accepts a maliciously controlled `assetId` and renders preview output. 2. The action does not enforce per-asset view authorization prior to returning preview content. 3. As a result, an authenticated user without asset-view permission can still obtain private preview output. This affects Craft installations with authenticated users of mixed privilege levels with private assets. ### Resources - d30df3112220db1ffd6726a3ed11857014c7fb27 - b1cddf72c98a
AI Analysis
Technical Summary
CVE-2026-56385 is an authorization bypass vulnerability affecting Craft CMS in versions >=4.0.0-RC1 and <=4.17.7, and >=5.0.0-RC1 and <=5.9.13. The issue exists in the assets/preview-file endpoint, where the system fails to enforce per-asset view authorization before returning preview content. As a result, an authenticated user with limited privileges can supply an arbitrary assetId and receive previewHtml content, including private preview image routes for assets they should not access. This vulnerability was addressed and fixed in Craft CMS versions 4.17.8 and 5.9.14.
Potential Impact
An authenticated low-privileged user can bypass authorization controls to view preview content of private assets they are not permitted to access. This exposure includes preview HTML and private preview image routes, potentially leaking sensitive asset information. The vulnerability does not require elevated privileges or user interaction beyond authentication.
Mitigation Recommendations
A fix is available in Craft CMS versions 4.17.8 and 5.9.14. Users should upgrade to these or later versions to remediate the vulnerability. No vendor advisory content was provided to indicate alternative mitigations or temporary fixes.
CVE-2026-56385: Authorization Bypass Through User-Controlled Key in craftcms cms
Description
### Summary An authenticated low-privileged user can call `assets/preview-file` for an asset they are not authorized to view and still receive preview response data (`previewHtml`) for that private asset. The returned preview HTML included a private preview image route containing the target private `assetId`, even though `canView` was `false` for the attacker account. ### Details 1. `assets/preview-file` accepts a maliciously controlled `assetId` and renders preview output. 2. The action does not enforce per-asset view authorization prior to returning preview content. 3. As a result, an authenticated user without asset-view permission can still obtain private preview output. This affects Craft installations with authenticated users of mixed privilege levels with private assets. ### Resources - d30df3112220db1ffd6726a3ed11857014c7fb27 - b1cddf72c98a
CVSS v4.0
Score 5.3medium
Affected software
craftcms
cms
pkg:github/craftcms/cmsRun on your own infrastructure? Check whether these packages are installed with threat-finder — our free open-source scanner.
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
CVE-2026-56385 is an authorization bypass vulnerability affecting Craft CMS in versions >=4.0.0-RC1 and <=4.17.7, and >=5.0.0-RC1 and <=5.9.13. The issue exists in the assets/preview-file endpoint, where the system fails to enforce per-asset view authorization before returning preview content. As a result, an authenticated user with limited privileges can supply an arbitrary assetId and receive previewHtml content, including private preview image routes for assets they should not access. This vulnerability was addressed and fixed in Craft CMS versions 4.17.8 and 5.9.14.
Potential Impact
An authenticated low-privileged user can bypass authorization controls to view preview content of private assets they are not permitted to access. This exposure includes preview HTML and private preview image routes, potentially leaking sensitive asset information. The vulnerability does not require elevated privileges or user interaction beyond authentication.
Mitigation Recommendations
A fix is available in Craft CMS versions 4.17.8 and 5.9.14. Users should upgrade to these or later versions to remediate the vulnerability. No vendor advisory content was provided to indicate alternative mitigations or temporary fixes.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- VulnCheck
- Date Reserved
- 2026-06-21T02:05:47.495Z
- Cvss Version
- 4.0
- State
- PUBLISHED
Threat ID: 6a37ed4baaf2dc2701b22769
Added to database: 06/21/2026, 13:55:23 UTC
Last enriched: 06/28/2026, 21:58:11 UTC
Last updated: 09/19/2026, 10:01:32 UTC
Views: 125
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