CVE-2026-8421 PUBLISHED

Concrete CMS 9.5.0 and below is vulnerable to CSRF on install_package() with conditional token bypass leading to RCE

Assigner: ConcreteCMS
Reserved: 12.05.2026 Published: 21.05.2026 Updated: 22.05.2026

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.

Metrics

CVSS 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
CVSS Score: 7.5

Product Status

Vendor Concrete CMS
Product Concrete CMS
Versions Default: unaffected
  • affected from 5.0 to 9.5.0 (incl.)

References

Problem Types

  • CWE-352 Cross-Site request forgery (CSRF) CWE

Impacts

  • CAPEC-193 PHP Remote File Inclusion