Vulnerability Description
Concrete CMS 9.5.0 and below contains a CSRF vulnerability in the install_package() method of concrete/controllers/single_page/dashboard/extend/install.php. An attacker who can cause an authenticated administrator to visit a crafted page, and who has placed or caused a package to be present under DIR_PACKAGES/<handle>/, can force the installation of that package without any CSRF protection. Package installation executes the package controller's install() method as the web server user, enabling remote code execution. In order to be vulnerable, the victim must be passing canInstallPackages. 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.
Related Weaknesses (CWE)
References
FAQ
What is CVE-2026-8421?
CVE-2026-8421 is a documented vulnerability. Concrete CMS 9.5.0 and below contains a CSRF vulnerability in the install_package() method of concrete/controllers/single_page/dashboard/extend/install.php. An attacker who can cause an authenticated...
How severe is CVE-2026-8421?
CVSS scoring is not yet available for CVE-2026-8421. Check NVD for updates.
Is there a patch for CVE-2026-8421?
Check the references section above for vendor advisories and patch information. Review vendor security bulletins for remediation guidance.