CVE-2026-55791Network attack vector

Unauthenticated SSRF and JavaScript injection via host poisoning

Published Jul 1, 2026 · Updated Jul 1, 2026

SSRF in Craft CMS 4.0.0-RC1 and later before 4.18.0, and 5.0.0-RC1 and later before 5.10.0, allows remote attackers to proxy content. The endpoint compares a URL against a base URL derived from attacker-controlled Host headers, then Guzzle fetches it and returns the body as JavaScript. The default trustedHosts setting enables header poisoning, but exploitation requires assetManager.cacheSourcePaths=false; a caching layer then serves stored script to control-panel users.

CVSS severity6.9
Medium
EPSS probability0.46%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

SSRF in Craft CMS 4.0.0-RC1 and later before 4.18.0, and 5.0.0-RC1 and later before 5.10.0, allows remote attackers to proxy content. The endpoint compares a URL against a base URL derived from attacker-controlled Host headers, then Guzzle fetches it and returns the body as JavaScript. The default trustedHosts setting enables header poisoning, but exploitation requires assetManager.cacheSourcePaths=false; a caching layer then serves stored script to control-panel users.

The record

CVE
CVE-2026-55791
Published
Jul 1, 2026
Updated
Jul 1, 2026
Vendor
Pixel & Tonic
Product
Craft CMS
Classifications
CWE-79, CWE-644, CWE-918, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jul 1, 2026CVE publishedPublication date reported by the CVE source.
  2. Jul 1, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=>= 4.0.0-RC1, < 4.18.0
  2. Affected versionversion=>= 5.0.0-RC1, < 5.10.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Pixel & Tonic · Craft CMSversion=>= 4.0.0-RC1, < 4.18.0; version=>= 5.0.0-RC1, < 5.10.0

Published CVSS scores

6.9GitHub, Inc. CNACVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N
9.2GitHub Advisory DatabaseCVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:L/SI:N/SA:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
CWE-644Improper Neutralization of HTTP Headers for Scripting Syntax
CWE-918Server-Side Request Forgery (SSRF)
T1190Exploit Public-Facing Application

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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