{"id":"CVE-2026-55791","summary":"Craft CMS: Blind SSRF and Arbitrary JavaScript Injection via Host Header Poisoning in actionResourceJs","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.","aliases":["GHSA-c55v-343g-5xff"],"modified":"2026-07-15T01:49:20.739936110Z","published":"2026-07-01T23:13:58.321Z","database_specific":{"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/55xxx/CVE-2026-55791.json","cna_assigner":"GitHub_M","cwe_ids":["CWE-644","CWE-79","CWE-918"]},"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"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/craftcms/cms","events":[{"introduced":"04755d93f86d07cc183db47db8a0eee106892e30"},{"fixed":"a516a6190ba8ef39a7603863df9ae09eb89f3a64"},{"introduced":"daac7c1da2f701f2e9ddee1da1457ce61660b581"},{"fixed":"f7fbf335ac15665372670b61046032f5f404f69a"}],"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"}}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-55791.json"}}],"schema_version":"1.7.5","severity":[{"type":"CVSS_V4","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"}]}