CVE-2026-8134
HIGHConcrete CMS 9.5.0 and below is vulnerable to Authenticated RCE via Composer customTemplate Path Traversal leading to PHP File Inclusion
Title source: cnaDescription
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.
References (1)
Core 1
Core References
Release Notes release-notes
https://documentation.concretecms.org/9-x/developers/introduction/version-history/951-release-notes
Scores
CVSS v3
7.2
EPSS
0.0074
EPSS Percentile
49.5%
Attack Vector
NETWORK
CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H
CISA SSVC
Vulnrichment
Exploitation
none
Automatable
no
Technical Impact
total
Details
CWE
CWE-23
CWE-434
CWE-98
Status
published
Products (2)
Concrete CMS/Concrete CMS
5.0 - 9.5.0
concretecms/concrete_cms
< 9.5.0
Published
May 21, 2026
Tracked Since
May 22, 2026