{
  "affected": [
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 5.9.14"
      },
      "package": {
        "ecosystem": "Packagist",
        "name": "craftcms/cms"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "5.0.0-RC1"
            },
            {
              "fixed": "5.9.15"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 4.17.8"
      },
      "package": {
        "ecosystem": "Packagist",
        "name": "craftcms/cms"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "4.0.0-RC1"
            },
            {
              "fixed": "4.17.9"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [],
  "database_specific": {
    "cwe_ids": [
      "CWE-918"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-04-14T23:36:09Z",
    "nvd_published_at": null,
    "severity": "MODERATE"
  },
  "details": "### Summary\n\nThe `resource-js` endpoint in Craft CMS allows unauthenticated requests to proxy remote JavaScript resources. \nWhen `trustedHosts` is not explicitly restricted (default configuration), the application trusts the client-supplied Host header. \n\nThis allows an attacker to control the derived `baseUrl`, which is used in prefix validation inside `actionResourceJs()`. \nBy supplying a malicious Host header, the attacker can make the server issue arbitrary HTTP requests, leading to Server-Side Request Forgery (SSRF).\n\n### Details\n\nThe vulnerability exists in `AppController::actionResourceJs()`.\n\nThe function validates that the `url` parameter starts with `assetManager-\u003ebaseUrl`. However, `baseUrl` is derived from the current request host. If `trustedHosts` is not configured, the Host header is fully attacker-controlled.\n\nAttack chain:\n\n1. Attacker sends request with controlled `Host` header.\n2. Application derives `baseUrl` from the malicious Host.\n3. `url` parameter is required to start with this `baseUrl`.\n4. Validation passes.\n5. Guzzle performs a server-side HTTP request to the attacker-controlled host.\n6. SSRF occurs.\n\nThis does not rely on string parsing bypass. It relies on Host header trust.\n\n### PoC (safe reproduction steps)\n\nEnvironment:\n- Craft CMS 5.9.12\n- Default configuration (no trustedHosts restriction)\n- Docker deployment\n\n1. Start a listener inside the container:\n   python3 -m http.server 9999\n\n2. Send a request to resource-js with a controlled Host header.\n\n3. Observe that the internal listener receives a request (OOB confirmation).",
  "id": "GHSA-95wr-3f2v-v2wh",
  "modified": "2026-04-14T23:36:10Z",
  "published": "2026-04-14T23:36:09Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/craftcms/cms/security/advisories/GHSA-95wr-3f2v-v2wh"
    },
    {
      "type": "WEB",
      "url": "https://github.com/craftcms/cms/commit/ebe7e85f1c89700d64332f72492be2e9a594e783"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/craftcms/cms"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:N/VC:H/VI:L/VA:N/SC:N/SI:N/SA:N/E:P",
      "type": "CVSS_V4"
    }
  ],
  "summary": "Craft CMS has a host header injection leading to SSRF via resource-js endpoint"
}