CVE-2026-8134Network attack vector

Authenticated code execution via custom template traversal

Published May 21, 2026 · Updated May 21, 2026

Path traversal in Concrete CMS 9.5.0 and earlier allows remote authenticated users to execute PHP code through a crafted custom template path. The page type composer layout saver accepts traversal sequences in ptComposerFormLayoutSetControlCustomTemplate and includes the resulting server-side file. Composer-form editing rights are required; an administrator can combine inclusion with extension-only upload validation to execute PHP stored under an image extension.

CVSS severity9.4
Critical
EPSS probability0.74%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Path traversal in Concrete CMS 9.5.0 and earlier allows remote authenticated users to execute PHP code through a crafted custom template path. The page type composer layout saver accepts traversal sequences in ptComposerFormLayoutSetControlCustomTemplate and includes the resulting server-side file. Composer-form editing rights are required; an administrator can combine inclusion with extension-only upload validation to execute PHP stored under an image extension.

The record

CVE
CVE-2026-8134
Published
May 21, 2026
Updated
May 21, 2026
Vendor
Concrete CMS
Product
Concrete CMS
Classifications
CWE-98, CWE-434, CWE-23, T1190
Attack vector
network
Privileges
admin

Timeline

How it unfolded

  1. May 21, 2026CVE publishedPublication date reported by the CVE source.
  2. May 21, 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=5.0 <=9.5.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesadmin

What is affected?

Concrete CMS · Concrete CMSversion=5.0 <=9.5.0

Published CVSS scores

9.4ConcreteCMSCVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H
7.2NIST NVDCVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H

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
Privilegesadmin
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-98Improper Control of Filename for Include/Require Statement in PHP Program ('PHP Remote File Inclusion')
CWE-434Unrestricted Upload of File with Dangerous Type
CWE-23Relative Path Traversal
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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