CVE-2026-55791

MEDIUMPre-NVD 6.96.9—
EchelonGraph scoreMEDIUM confidence

This medium-severity CVE scores 6.9 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.3%, top 75% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: epss, secondary
Trending — 3 sources updated this week
6.9
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS: 0%CVSS: 6.9Exploit: NoneExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

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.

CVSS v3
6.9
EG Score
6.9(medium)
EPSS
25.0%
KEV
Not listed

Published

June 19, 2026

Last Modified

July 2, 2026

Advisory Details (2)

Auto-updated Jul 3, 2026
Patch available. Sources: github_pr, github.
github Patch Available

Blind SSRF and Arbitrary JavaScript Injection via Host Header Poisoning in actionResourceJs · Advisory · craftcms/cms · GitHub

https://github.com/craftcms/cms/security/advisories/GHSA-c55v-343g-5xff
github_pr Patch Available

Enforce appended script ordering

Patch available: craftcms/cms 4.18.0 (PR #18559 merged 2026-04-21)

https://github.com/craftcms/cms/pull/18559

Vendor Advisories for CVE-2026-55791(1)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Affected Packages

(1 across 1 ecosystem)
Packagist(1)
PackageVulnerable rangeFixed inDependents
craftcms/cms4.0.0 ... 4.9.7 (249 versions)4.18—

Weakness Classification(3)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 14× in last 7d / 15× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

  1. 2026-07-06 16:27 UTCEPSS rescore
  2. 2026-07-06 16:27 UTCEPSS rescore
  3. 2026-07-06 05:15 UTCEG score recompute
  4. 2026-07-06 02:23 UTCEPSS rescore
  5. 2026-07-06 02:23 UTCEPSS rescore
  6. 2026-07-05 04:18 UTCEG score recompute
  7. 2026-07-05 02:31 UTCEPSS rescore
  8. 2026-07-05 02:30 UTCEPSS rescore
  9. 2026-07-04 06:31 UTCEPSS rescore
  10. 2026-07-04 06:31 UTCEPSS rescore
  11. 2026-07-04 03:17 UTCEG score recompute
  12. 2026-07-03 02:15 UTCEG score recompute
  13. 2026-07-02 01:22 UTCEG score recompute▲ 6.90
  14. 2026-07-02 01:21 UTCNVD updateCVSS v3 → 6.9 · CVSS v4 → 6.9 · severity → MEDIUM
  15. 2026-06-19 21:23 UTCEG score recompute

Related CVEs(same CWE)

Frequently asked(5)

What is CVE-2026-55791?
CVE-2026-55791 is a medium vulnerability published on June 19, 2026. 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…
When was CVE-2026-55791 disclosed?
CVE-2026-55791 was first published in the National Vulnerability Database on June 19, 2026, with the most recent update on July 2, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-55791 actively exploited?
CVE-2026-55791 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 25.0% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2026-55791?
CVE-2026-55791 has a CVSS v3 base score of 6.9 (NVD).
How do I remediate CVE-2026-55791?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-55791, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

Dependency Blast Radius

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