CVE-2026-55791
Description
Craft CMS is a content management system (CMS). Versions 4.0.0-RC1 and above, prior to 4.18.0 and 5.0.0-RC1, and above, prior to 5.10.0, are vulnerable to Server-Side Request Forgery (SSRF) and Arbitrary JavaScript Injection through the /actions/app/resource-js endpoint. By exploiting the default permissive trustedHosts configuration, an attacker can poison the Host or X-Forwarded-Host header to manipulate the application’s $baseUrl. This bypasses the endpoint’s internal URL validation, forcing the backend Guzzle client to fetch a malicious payload from an attacker-controlled server and reflect it to the client with a Content-Type: application/javascript header. The vulnerability manifests when assetManager.cacheSourcePaths is set to false. This issue has been fixed in versions 4.18.0 and 5.10.0.
How to fix
- craftcms/cms5.10, 4.18 or later
Affected products
| Product | Affected versions | Fixed in |
|---|---|---|
| craftcms/cmsPackagist | 5.0.0-RC1 ≤ v < 5.10, 4.0.0-RC1 ≤ v < 4.18 | 5.10, 4.18 |
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Attack Surface Management
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