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Description

Concrete CMS 9.5.0 and below emits a CSRF token in the local_available_update.php view ($token->output('do_update')) but the corresponding do_update() method in concrete/controllers/single_page/dashboard/system/update/update.php never calls $this->token->validate('do_update'). The form is rendered as a POST form, meaning the token reaches the browser, but because the controller discards it without verification, an attacker can craft a cross-site POST that triggers a core CMS update to an attacker-specified version string. In order to be vulnerable, theictim must be passing canUpgrade()anda valid update version must be present under DIR_CORE_UPDATES. 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.

PUBLISHED Reserved 2026-05-12 | Published 2026-05-21 | Updated 2026-05-22 | Assigner ConcreteCMS




HIGH: 7.5CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:A/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

Problem types

CWE-352 Cross-Site request forgery (CSRF)

CWE-829 Inclusion of functionality from untrusted control sphere

Product status

Default status
unaffected

5.0 (git)
affected

References

documentation.concretecms.org/...n-history/951-release-notes release-notes

cve.org (CVE-2026-8428)

nvd.nist.gov (CVE-2026-8428)

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