CVE-2026-8426
HighSummary
Concrete CMS versions 9.5.0 and below do not validate a CSRF token before processing requests to /dashboard/extend/update/prepare_remote_upgrade/<remoteMPID>. An attacker controlling the remote package for a known marketplace item ID can overwrite the PHP package on disk and force its upgrade() method to execute in a single browser navigation.
Risk Assessment
This vulnerability can lead to remote code execution as the web server user, posing a significant security risk to the organization. It requires the victim to have canInstallPackages enabled and to be connected to the Concrete marketplace.
Recommendation
It is recommended to update Concrete CMS to a version above 9.5.0 and implement additional CSRF token validation mechanisms in the application. Monitoring and restricting access to remote packages should also be considered.
Original NVD description (English source)
Concrete CMS 9.5.0 and below does not validate a CSRF token before processing requests to /dashboard/extend/update/prepare_remote_upgrade/<remoteMPID>. An attacker who controls the remote package returned for a known marketplace item ID can overwrite the package PHP on disk and force its upgrade() method to execute in a single browser navigation. This results in remote code execution as the web server user. In order to be vulnerable, the victim must be passing canInstallPackages, victim site must be connected to the Concrete marketplace; and the attacker controls the package returned for a marketplace item ID already installed on the victim site. The Concrete CMS security team gave this vulnerability a CVSS v.4.0 score of 7.5 with vector CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:A/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N. Thanks https://github.com/maru1009 for reporting.