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:
- The endpoint accepts an attacker-controlled
assetId. - Asset is resolved, and thumbnail HTML is returned.
- No explicit asset-view permission check is performed before preview generation.
Impact
Type:
- Missing authorization
- Unauthorized preview-link disclosure
Affected deployments:
- Craft sites with control panel users who have partial permissions and private assets.
Security consequence:
- A control panel user without asset-view permission can still obtain signed preview transform link data for private assets.
- This may increase private asset exposure risk depending on deployment and endpoint chaining.
Resources
https://github.com/craftcms/cms/commit/d30df3112220db1ffd6726a3ed11857014c7fb27
Software afectado
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| Plataforma | Paquete | Versiones vulnerables | Corregida en |
|---|---|---|---|
| Paquete de Composer | craftcms/cms | >= 4.0.0-RC1, < 4.17.8, >= 5.0.0-RC1, < 5.9.14 | 4.17.8, 5.9.14 |
Referencias
- https://github.com/craftcms/cms/security/advisories/GHSA-x76w-8c62-48mg
- https://nvd.nist.gov/vuln/detail/CVE-2026-56384
- https://github.com/craftcms/cms/commit/d30df3112220db1ffd6726a3ed11857014c7fb27
- https://github.com/craftcms/cms
- https://www.vulncheck.com/advisories/craft-cms-missing-authorization-in-assets-preview-thumb-endpoint
- Vector CVSS
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- Debilidad (CWE)
CWE-200, CWE-862- Plataforma
- Composer
- Paquete
craftcms/cms- Publicada
- 06.07.2026
- Actualizado
- 11.10.2026 10:22
Fuentes y licencias
OSV / GitHub Advisory Database - GHSA-x76w-8c62-48mg - CC BY 4.0
Historial de vulnerabilidades: craftcms/cms
Todas las vulnerabilidades publicadas de este paquete (Paquete de Composer), de la más reciente a la más antigua. Muestra si es un fallo aislado o un paquete que hay que vigilar.
- Entradas en total
- 127
- Primera → última
- 07.2021 08.2026
- Sin corrección
- 6
- Explotada en ataques
- 4
Distribución por gravedad
- Crítica 9
- Alta 41
- Media 65
- Baja 12
Divulgaciones por año
- 2021: 3
- 2022: 22
- 2023: 13
- 2024: 9
- 2025: 6
- 2026: 74
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Craft CMS: Authenticated "assets/preview-thumb" discloses signed fallback transform preview link to CP users without asset-view permission esta entrada
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