{
  "affected": [
    {
      "ranges": [
        {
          "database_specific": {
            "extracted_events": [
              {
                "introduced": "5.0.0-RC1"
              },
              {
                "fixed": "5.10.0"
              },
              {
                "introduced": "4.0.0-RC1"
              },
              {
                "fixed": "4.18.0"
              }
            ],
            "source": "AFFECTED_FIELD"
          },
          "events": [
            {
              "introduced": "04755d93f86d07cc183db47db8a0eee106892e30"
            },
            {
              "fixed": "a516a6190ba8ef39a7603863df9ae09eb89f3a64"
            },
            {
              "introduced": "daac7c1da2f701f2e9ddee1da1457ce61660b581"
            },
            {
              "fixed": "f7fbf335ac15665372670b61046032f5f404f69a"
            }
          ],
          "repo": "https://github.com/craftcms/cms",
          "type": "GIT"
        }
      ]
    }
  ],
  "aliases": [
    "GHSA-c55v-343g-5xff"
  ],
  "database_specific": {
    "cna_assigner": "GitHub_M",
    "cwe_ids": [
      "CWE-644",
      "CWE-79",
      "CWE-918"
    ],
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/55xxx/CVE-2026-55791.json"
  },
  "details": "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.",
  "id": "CVE-2026-55791",
  "modified": "2026-07-08T05:36:55.502462449Z",
  "published": "2026-07-01T23:13:58.321Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/55xxx/CVE-2026-55791.json"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/craftcms/cms/security/advisories/GHSA-c55v-343g-5xff"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-55791"
    },
    {
      "type": "FIX",
      "url": "https://github.com/craftcms/cms/pull/18559"
    }
  ],
  "schema_version": "1.7.5",
  "severity": [
    {
      "score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N",
      "type": "CVSS_V4"
    }
  ],
  "summary": "Craft CMS: Blind SSRF and Arbitrary JavaScript Injection via Host Header Poisoning in actionResourceJs"
}