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: 0.5%, top 61% 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
6.9EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0.5%CVSS: 6.9Exploit: None knownExposed services: Not assessed

A fix is available — apply it.

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
6.9MEDIUMmedium confidence
EG Risk
36
EG Risk 36/100

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity69% × 45%
Exploitation0% × 40%
Automatability30% × 15%
EPSS PROB
0.5%
EPSS %ILE
38th
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.
githubMentions a patch (unverified)

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 rangeFix by version rangeDependents
craftcms/cms4.0.0 ... 4.9.7 (249 versions)
  • 5.0.0-RC1 up to 5.10: fixed in 5.10
  • 4.0.0-RC1 up to 4.18: fixed in 4.18
—

Weakness Classification(3)

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

Data Freshness Timeline

(refreshed 6× in last 7d / 26× 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.

Showing the most recent 100 of 128 total refreshes for this CVE.

  1. 2026-10-09 20:07 UTCEPSS rescore
  2. 2026-10-08 17:12 UTCEPSS rescore
  3. 2026-10-07 23:48 UTCEPSS rescore
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  1. 2026-09-11 14:53 UTCEPSS rescore
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  27. 2026-08-18 13:48 UTCEPSS rescore
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  45. 2026-08-07 19:30 UTCEG score recompute
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  68. 2026-07-23 03:20 UTCEG score recompute
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  74. 2026-07-19 02:29 UTCEPSS rescore
  75. 2026-07-18 10:04 UTCEPSS rescore

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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 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 0.5% probability of exploitation in the next 30 days (38th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-55791?
CVE-2026-55791 has a CVSS base score of 6.9 (a secondary CVSS source that NVD displays; NVD's own analysis pending).
How do I remediate CVE-2026-55791?
A fix for CVE-2026-55791 is available: update to the fixed version the vendor names in its advisory. The vendor advisories EchelonGraph has for CVE-2026-55791 are linked in the Vendor Advisories panel on this page.

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