CVE-2026-8134

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.

PUBLISHED Reserved 2026-05-07 | Published 2026-05-21 | Updated 2026-05-22 | Assigner ConcreteCMS

Problem types

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

Product status

Credits

Yonatan Drori (Tenzai) finder

References

documentation.concretecms.org/...n-history/951-release-notes release-notes

cve.org (CVE-2026-8134)

nvd.nist.gov (CVE-2026-8134)

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