VIR Vulnerability Intelligence Relay

CVE-2026-8421

high
Published 2026-05-21 · Modified 2026-05-26
CVSS v3
8.8
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
CVSS v2
—
VIR risk
8.8

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.

Predictions

Exploit likelihood
92%
Patch ETA
—

Heuristic predictions, AS-IS, for prioritization only.

Mitigations

vendor Authored 2026-05-27

Vendor advisory: ff5b8ace-8b95-4078-9743-eac1ca5451de — https://documentation.concretecms.org/9-x/developers/introduction/version-history/951-release-notes

Application impact
VendorProductVersionsFixed
concretecmsconcrete_cms{"endExcluding":"9.5.1"}9.5.1

References

CWEs

CWE-352

Verify integrity in audit chain (admin only). AS-IS.