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TI-2026-40277 Aliases CVE-2026-55791GHSA-c55v-343g-5xff

Craft CMS: Blind SSRF and Arbitrary JavaScript Injection via Host Header Poisoning in actionResourceJs

Priority LOW 37CWE-644Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
None
Attack complexity
Low
Attack requirements
None
Impact type
Cross-site scripting, Information disclosure, Security bypass
Confidentiality · integrity · availability
Low · None · None
Fix status
Fixed

Attack profile from CVSS 4.0 · CNA. Fix status from CNA and GitHub. Impact type from CWE-79, CWE-918, CWE-346 and the CVSS impact.

Summary

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.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00464 40th percentileScored 2026-11-07
Fix Fixed cms (craftcms): 5.10.0, 4.18.0craftcms/cms (Packagist): 5.10, 4.18

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
None
Automatable
Yes
Technical impact
Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
Craft CMScms5.0.0-RC1 to before 5.10.0; 4.0.0-RC1 to before 4.18.05.10.0, 4.18.0Patch availableCNA
—craftcms/cms (Packagist)5.0.0-RC1 to before 5.105.10Patch availableGHSA-c55v-343g-5xff
—craftcms/cms (Packagist)4.0.0-RC1 to before 4.184.18Patch availableGHSA-c55v-343g-5xff
  • cms VendorCraft CMS Affected 5.0.0-RC1 to before 5.10.0; 4.0.0-RC1 to before 4.18.0 Fixed in 5.10.0, 4.18.0 Patch available CNA
  • craftcms/cms (Packagist) Vendor— Affected 5.0.0-RC1 to before 5.10 Fixed in 5.10 Patch available GHSA-c55v-343g-5xff
  • craftcms/cms (Packagist) Vendor— Affected 4.0.0-RC1 to before 4.18 Fixed in 4.18 Patch available GHSA-c55v-343g-5xff

CPE names Threatist (inferred) · 1

Inferred from how NVD named this product before; not given by a source.

CPEVersionsRoleVendor
cpe:2.3:a:craftcms:craft_cms:*:*:*:*:*:*:*:*——Craft CMS
  • cpe:2.3:a:craftcms:craft_cms:*:*:*:*:*:*:*:* Versions — — ·Craft CMS

Remediation

  • Fix · CNA cms (craftcms) Fixed in 5.10.0, 4.18.0
  • Fix · GHSA-c55v-343g-5xff craftcms/cms (Packagist) Fixed in 5.10 Advisory →
  • Fix · GHSA-c55v-343g-5xff craftcms/cms (Packagist) Fixed in 4.18 Advisory →

Timeline

  1. 2026-10-02 Threatist record created from CVE-2026-55791
  2. 2026-10-03 Alias added: GHSA-c55v-343g-5xff

References

Other 3

  • TI-2025-23503 Craft CMS Allows Remote Code Execution KEVCVSS 3.1CRITICAL 10.0
  • TI-2024-37138 RCE when PHP `register_argc_argv` config setting is enabled in craftcms/cms KEVCVSS 4.0CRITICAL 9.3
  • TI-2025-16994 Potential RCE with a compromised security key in craft/cms KEVCVSS 3.1HIGH 8.1
  • TI-2025-24595 Craft CMS stores user-provided content in session files KEVCVSS 4.0MEDIUM 6.9
  • TI-2023-22284 Craft CMS Remote Code Execution vulnerability CVSS 3.1CRITICAL 10.0
  • TI-2024-25171 Craft CMS up to v3.7.31 was discovered to contain a SQL injection vulnerability via the GraphQL API endpoint. CVSS 3.1CRITICAL 9.8
See all 203 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences