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.
CVSS Score
HIGH
Affected Products
| Vendor | Product | Versions |
|---|---|---|
| Concretecms | Concrete Cms | < 9.5.1 |
Related Weaknesses (CWE)
References
FAQ
What is CVE-2026-8421?
CVE-2026-8421 is a vulnerability with a CVSS score of 8.8 (HIGH). 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?
CVE-2026-8421 has been rated HIGH with a CVSS base score of 8.8/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2026-8421?
Check the references section above for vendor advisories and patch information. Affected products include: Concretecms Concrete Cms.