Craft CMS: Authenticated "assets/preview-thumb" discloses signed fallback transform preview link to CP users without asset-view permission
### Summary A user with Control Panel access but without permission to view a target private asset can call `assets/preview-thumb` and receive preview HTML that contains a signed fallback transform link for that private asset. ### Details Root-cause analysis: 1. The endpoint accepts an attacker-controlled `assetId`. 2. Asset is resolved, and thumbnail HTML is returned. 3. No explicit asset-view permission check is performed before preview generation. ### Impact Type: 1. Missing authorization 2. Unauthorized preview-link disclosure Affected deployments: 1. Craft sites with control panel users who have partial permissions and private assets. Security consequence: 1. A control panel user without asset-view permission can still obtain signed preview transform link data for private assets. 2. This may increase private asset exposure risk depending on deployment and endpoint chaining. ## Resources https://github.com/craftcms/cms/commit/d30df3112220db1ffd6726a3ed11857014c7fb27
AI Analysis
Technical Summary
The vulnerability in Craft CMS involves the assets/preview-thumb endpoint accepting an attacker-controlled assetId parameter and returning thumbnail HTML containing a signed fallback transform link for that asset. The root cause is the lack of an explicit asset-view permission check before preview generation. Consequently, control panel users without permission to view certain private assets can still obtain signed preview transform link data, leading to unauthorized preview-link disclosure and missing authorization controls.
Potential Impact
Control panel users without permission to view private assets can obtain signed preview transform links, which may increase the risk of private asset exposure. The impact depends on the deployment and whether additional endpoint chaining or access methods can leverage this information. There is no indication of remote unauthenticated exploitation or privilege escalation beyond the existing control panel user privileges.
Mitigation Recommendations
Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Until a fix is available, restrict control panel user permissions carefully to minimize exposure. Monitor vendor communications for updates addressing this authorization bypass issue.
Craft CMS: Authenticated "assets/preview-thumb" discloses signed fallback transform preview link to CP users without asset-view permission
Description
### Summary A user with Control Panel access but without permission to view a target private asset can call `assets/preview-thumb` and receive preview HTML that contains a signed fallback transform link for that private asset. ### Details Root-cause analysis: 1. The endpoint accepts an attacker-controlled `assetId`. 2. Asset is resolved, and thumbnail HTML is returned. 3. No explicit asset-view permission check is performed before preview generation. ### Impact Type: 1. Missing authorization 2. Unauthorized preview-link disclosure Affected deployments: 1. Craft sites with control panel users who have partial permissions and private assets. Security consequence: 1. A control panel user without asset-view permission can still obtain signed preview transform link data for private assets. 2. This may increase private asset exposure risk depending on deployment and endpoint chaining. ## Resources https://github.com/craftcms/cms/commit/d30df3112220db1ffd6726a3ed11857014c7fb27
CVSS v4.0
Affected software
Run 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
The vulnerability in Craft CMS involves the assets/preview-thumb endpoint accepting an attacker-controlled assetId parameter and returning thumbnail HTML containing a signed fallback transform link for that asset. The root cause is the lack of an explicit asset-view permission check before preview generation. Consequently, control panel users without permission to view certain private assets can still obtain signed preview transform link data, leading to unauthorized preview-link disclosure and missing authorization controls.
Potential Impact
Control panel users without permission to view private assets can obtain signed preview transform links, which may increase the risk of private asset exposure. The impact depends on the deployment and whether additional endpoint chaining or access methods can leverage this information. There is no indication of remote unauthenticated exploitation or privilege escalation beyond the existing control panel user privileges.
Mitigation Recommendations
Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Until a fix is available, restrict control panel user permissions carefully to minimize exposure. Monitor vendor communications for updates addressing this authorization bypass issue.
Technical Details
- Gcve Source
- db.gcve.eu
- Osv Id
- GHSA-x76w-8c62-48mg
- Osv Schema Version
- 1.4.0
- Aliases
- []
- Ecosystems
- ["Packagist"]
- Database Specific Severity
- MODERATE
- Cvss Version
- 4.0
Threat ID: 6a4c340627e9c797195f674f
Added to database: 07/06/2026, 23:02:30 UTC
Last enriched: 07/06/2026, 23:14:47 UTC
Last updated: 07/31/2026, 12:27:30 UTC
Views: 58
Community Reviews
0 reviewsCrowdsource mitigation strategies, share intel context, and vote on the most helpful responses. Sign in to add your voice and help keep defenders ahead.
Want to contribute mitigation steps or threat intel context? Sign in or create an account to join the community discussion.
Actions
Updates to AI analysis require Pro Console access. Upgrade inside Console → Billing.
External Links
Need more coverage?
Upgrade to Pro Console for AI refresh and higher limits.
For incident response and remediation, OffSeq services can help resolve threats faster.
Latest Threats
Check if your credentials are on the dark web
Instant breach scanning across billions of leaked records. Free tier available.