CVE-2026-8134

Concrete CMS 9.5.0 and below is vulnerable to Authenticated RCE via Composer customTemplate Path Traversal leading to PHP File Inclusion

State: Published
Severity: 9.4 Critical
Published: May 21, 2026
Updated: May 22, 2026
Reserved: May 7, 2026

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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.

Scores

CVSS	Score	Vector	Source
4.0	9.4 Critical	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	ConcreteCMS

Weaknesses

CWE-98 Improper control of filename for Include/Require statement in PHP program ('PHP remote file inclusion')
CWE-434 Unrestricted upload of file with dangerous type
CWE-23 Relative path traversal

Affected Products

Product	Versions
Concrete CMSConcrete CMS	5.0 through 9.5.0Affected

References

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

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