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CVE-2026-41130 — craftcms/cms

Fix: craftcms/cms@ebe7e85

CVE-2026-41130 is a Server-Side Request Forgery (SSRF) vulnerability in craftcms/cms. A fix is available for craftcms/cms — see the affected versions and patch details below.

Craft CMS has a host header injection leading to SSRF via resource-js endpoint

Also known asGHSA-95wr-3f2v-v2wh
Published
Apr 21, 2026
Updated
Aug 12, 2026
Affected
2 pkgs
Patched
2 / 2
Exploits
None indexed
Exploitation data as of Sep 22, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

Proof-of-concept exploit code exists

  • CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
  • CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.

Exploitation and automatability from CISA’s SSVC triage for CVE-2026-41130.

EPSS Exploitation Probability

via FIRST.org ↗
0.3%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs18th percentile — riskier than 18% of all scored CVEsHighest risk

EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.

Real-World Exposure

2 pkgs affected
🐘craftcms/cms🐘craftcms/cms

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Packagist packages — download data is not available via public APIs for these ecosystems.

Description

Summary

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:

  1. Attacker sends request with controlled Host header.
  2. Application derives baseUrl from the malicious Host.
  3. url parameter is required to start with this baseUrl.
  4. Validation passes.
  5. Guzzle performs a server-side HTTP request to the attacker-controlled host.
  6. 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

  1. Start a listener inside the container: python3 -m http.server 9999

  2. Send a request to resource-js with a controlled Host header.

  3. Observe that the internal listener receives a request (OOB confirmation).

Affected Packages

2 total 2 fixed
EcosystemPackageVulnerable rangeFix
🐘Packagistcraftcms/cms≥ 5.0.0-RC1&&< 5.9.155.9.15composer require craftcms/cms:^5.9.15
🐘Packagistcraftcms/cms≥ 4.0.0-RC1&&< 4.17.94.17.9composer require craftcms/cms:^4.17.9

Detection & mitigation playbook

Open-source dependency

  1. Detect

    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for craftcms/cms, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

  2. Fix

    Update craftcms/cms to 5.9.15 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-41130 is resolved across your whole dependency graph.

  3. Workarounds

    If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

  4. How O3 protects you

    O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2026-41130 can be triaged on real exposure rather than presence alone.

Tailored to CVE-2026-41130. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.

Frequently Asked Questions

### Summary 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::actionResource
O3 Security · Impact-Aware SCA

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CVE-2026-41130: craftcms/cms SSRF | O3 Security