CVE-2026-8134: Concrete CMS Vulnerable to Relative Path Traversal
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.
Published May 21, 2026 · Updated Jun 23, 2026
Affected packages
concrete5/concrete5
- Ecosystem
- Composer (PHP)
- Affected
- < 9.5.1
- Fixed in
- 9.5.1
- Check
composer show concrete5/concrete5
Advisory details
From the GitHub Advisory Database (CC BY 4.0).
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. Concrete CMS thanks Yonatan Drori (Tenzai) for reporting this issue.
References
How this page is made: the data panel comes from the GitHub Advisory Database, CISA’s KEV catalog, the NVD and FIRST EPSS, and updates twice a day. No analysis has been written for this entry yet. Methodology