CVE-2026-8134

CRITICAL EPSS 49.9%

Published May 21, 20261mo ago · Modified Jun 17, 20261w ago

9.4 CVSS 4.0

Critical

Published May 21, 2026 1mo ago

Last Modified Jun 17, 2026 1w ago

Description

Concrete CMS 9.5.0 and below fails to sanitize path traversal sequences in the ptComposerFormLayoutSetControlCustomTemplate field when saving page type composer form layouts. An authenticated rogue administrator with composer form editing rights can exploit this to include arbitrary readable files on the server. Combined with the file uploader's extension-only validation (which permits PHP code in files saved with image extensions like .png), this can result in authenticated remote code execution. The Concrete CMS security team gave this vulnerability a CVSS v.4.0 score of 9.4 with vector CVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H Thanks Yonatan Drori (Tenzai) for reporting.

CVSS Details

Base Score

9.4

Exploitability

—

Impact

—

Vector string

CVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Attack Vector Network

Attack Complexity Low

Privileges Required High

User Interaction None

Scope X

Threat Intelligence

EPSS Exploit Probability

49.9% percentile

Exploit & Patch Status

No Known Exploit

No Patch Available

Weaknesses 3

CWE-23

CWE-434 Unrestricted Upload of File with Dangerous Type Resource Mgmt

CWE-98

Affected Products 1

Vendor	Product	Version	Range
concretecms	concrete_cms	*	≤9.5.0

References 1

documentation.concretecms.org https://documentation.concretecms.org/9-x/developers/introduction/version-history/951-release-notes

Release Notes

Remediation

No remediation data recorded yet

Check vendor advisories and the NVD entry for patch availability.