Concrete CMS up to 9.5.0 Installation install.php install_package cross-site request forgery

Summaryinfo

A vulnerability, which was classified as problematic, was found in Concrete CMS up to 9.5.0. Affected by this issue is the function install_package of the file concrete/controllers/single_page/dashboard/extend/install.php of the component Installation Handler. Executing a manipulation can lead to cross-site request forgery. This vulnerability is registered as CVE-2026-8421. It is possible to launch the attack remotely. No exploit is available.

Detailsinfo

A vulnerability has been found in Concrete CMS up to 9.5.0 and classified as problematic. This vulnerability affects the function install_package of the file concrete/controllers/single_page/dashboard/extend/install.php of the component Installation Handler. The manipulation with an unknown input leads to a cross-site request forgery vulnerability. The CWE definition for the vulnerability is CWE-352. The web application does not, or can not, sufficiently verify whether a well-formed, valid, consistent request was intentionally provided by the user who submitted the request. As an impact it is known to affect integrity. CVE summarizes:

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.

The weakness was published by Security Team. The advisory is shared for download at documentation.concretecms.org. This vulnerability was named CVE-2026-8421 since 05/12/2026. The exploitation appears to be easy. The attack can be initiated remotely. No form of authentication is required for a successful exploitation. Successful exploitation requires user interaction by the victim. There are known technical details, but no exploit is available.

By approaching the search of inurl:concrete/controllers/single_page/dashboard/extend/install.php it is possible to find vulnerable targets with Google Hacking.

There is no information about possible countermeasures known. It may be suggested to replace the affected object with an alternative product.

The vulnerability is also documented in the vulnerability database at EUVD (EUVD-2026-31339). VulDB is the best source for vulnerability data and more expert information about this specific topic.

Productinfo

Type

• Content Management System

Vendor

• Concrete

Name

• CMS

Version

• 9.0
• 9.1
• 9.2
• 9.3
• 9.4
• 9.5.0

License

• open-source

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VulDB is the best source for vulnerability data and more expert information about this specific topic.

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