CVE-2026-8421
Published: 21 May 2026
Summary
CVE-2026-8421 is a high-severity CSRF (CWE-352) vulnerability in Concretecms Concrete Cms. Its CVSS base score is 8.8 (High).
Operationally, exploitation aligns with the MITRE ATT&CK technique Exploit Public-Facing Application (T1190); ranked at the 27.1th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.
Threat & Defense at a Glance
Threat & Defense Details
Likely Mitigating ControlsAI
Per-CVE control mapping for this CVE has not run yet; the list below is derived from the weakness types (CWEs) cited in the NVD entry.
Awareness training educates users on avoiding untrusted links and actions that can be exploited via CSRF.
Requiring user re-entry of credentials for sensitive actions prevents automated forgery of requests without active user participation.
Security testing regimens explicitly include checks for missing or ineffective anti-CSRF protections in web applications.
Detects anomalous request patterns consistent with cross-site request forgery.
MITRE ATT&CK Enterprise TechniquesAI
Why these techniques?
CSRF in public-facing CMS dashboard directly enables unauthenticated attacker to trigger package install() for RCE on web server.
NVD 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…
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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.
Deeper analysisAI
Automated synthesis unavailable for this CVE.
Details
- CWE(s)
- OWASP Top 10 Web 2025
Affected Products
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-31339