CVE-2026-8134
Concrete CMS versions 9.5.0 and earlier allow an authenticated administrator with composer form editing rights to save page layouts that include path traversal sequences. This flaw lets the attacker read any file on the server and, when combined with the file uploader’s weak validation, can lead to remote code execution.
No official fix yet. If none appears within 45 days of first tracking, this entry is removed automatically.
Who is affected
Concrete CMS 9.5.0 and earlier, specifically users who are administrators or have composer form editing permissions.
Real-world impact
An attacker who can log in as an administrator can read arbitrary files on the server and, by uploading a file with a PHP payload disguised as an image, can run that code on the server, effectively taking control of the site.
Why this severity
The CVSS score of 9.4 reflects that the vulnerability requires high privileges (administrator), is exploitable over the network, and provides complete compromise of confidentiality, integrity, and availability. The ability to execute arbitrary code remotely makes it a critical risk.
What to do about it
No official fix or mitigation is documented in the sources yet. Monitor the vendor advisory and apply the patch as soon as it is released.
No fix documented in sources
Timeline
- May 21, 2026 · May 21, 2026PublishedDisclosed and added to the National Vulnerability Database.
- Jul 23, 2026 · 12d agoAdvisory updatedThe NVD record was last revised.