Is CVE-2026-8421 actively exploited?

No active exploitation of CVE-2026-8421 has been confirmed so far. Continue monitoring, as exploit status can change.

Can CVE-2026-8421 be exploited remotely?

Yes. CVE-2026-8421 is exploitable remotely over the network (CVSS attack vector: Network).

What is the CVSS score of CVE-2026-8421?

CVE-2026-8421 has a CVSS score of 8.8 (HIGH).

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HIGH

CVE-2026-8421

CWE-352Published: May 21, 2026· Updated: May 26, 2026

8.8

CVSS v3.1

EPSS:0.09%probability of exploitation in 30 daysPercentile:24.6th

Official 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.

NVD Source

Technical Analysis

CVE-2026-8421 can be exploited remotely over the network without requiring physical or adjacent access, significantly expanding the attack surface for threat actors.

Exploitation does not require any privileges, though user interaction (Required) is needed, which slightly reduces the risk of mass automated attacks.

A successful exploit results in complete confidentiality breach (data exposure), full integrity compromise (data manipulation), availability disruption (denial of service), with a CVSS base score of 8.8.