Summary
Craft CMS has a host header injection leading to SSRF via resource-js endpoint
The resource-js endpoint in Craft CMS allows unauthenticated requests to proxy remote JavaScript resources.
When trustedHosts is not explicitly restricted (default configuration), the application trusts the client-supplied Host header.
This allows an attacker to control the derived baseUrl, which is used in prefix validation inside actionResourceJs().
By supplying a malicious Host header, the attacker can make the server issue arbitrary HTTP requests, leading to Server-Side Request Forgery (SSRF).
Details
The vulnerability exists in AppController::actionResourceJs().
The function validates that the url parameter starts with assetManager->baseUrl. However, baseUrl is derived from the current request host. If trustedHosts is not configured, the Host header is fully attacker-controlled.
Attack chain:
- Attacker sends request with controlled
Hostheader. - Application derives
baseUrlfrom the malicious Host. urlparameter is required to start with thisbaseUrl.- Validation passes.
- Guzzle performs a server-side HTTP request to the attacker-controlled host.
- SSRF occurs.
This does not rely on string parsing bypass. It relies on Host header trust.
PoC (safe reproduction steps)
Environment:
- Craft CMS 5.9.12
- Default configuration (no trustedHosts restriction)
- Docker deployment
Start a listener inside the container:
python3 -m http.server 9999Send a request to resource-js with a controlled Host header.
Observe that the internal listener receives a request (OOB confirmation).
Impact
Untrusted input controls the target URL of a server-initiated request, which may reach internal services not otherwise accessible from outside. Typical impact: access to internal metadata services, internal APIs, or cloud credentials.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
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craftcms/cms to 5.9.15 or later; craftcms/cms to 4.17.9 or later
Kodem Kai can prioritize this vulnerability in your dependency tree and generate a fix recommendation.
Frequently Asked Questions
- What is CVE-2026-41130? CVE-2026-41130 is a medium-severity server-side request forgery (SSRF) vulnerability in craftcms/cms (composer), affecting versions >= 5.0.0-RC1, <= 5.9.14. It is fixed in 5.9.15, 4.17.9. Untrusted input controls the target URL of a server-initiated request, which may reach internal services not otherwise accessible from outside.
- Which versions of craftcms/cms are affected by CVE-2026-41130? craftcms/cms (composer) versions >= 5.0.0-RC1, <= 5.9.14 is affected.
- Is there a fix for CVE-2026-41130? Yes. CVE-2026-41130 is fixed in 5.9.15, 4.17.9. Upgrade to this version or later.
- Is CVE-2026-41130 exploitable, and should I be worried? Whether CVE-2026-41130 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2026-41130 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2026-41130?
- Upgrade
craftcms/cmsto 5.9.15 or later - Upgrade
craftcms/cmsto 4.17.9 or later
- Upgrade