CVE-2026-8340: Concrete CMS 9.5.0 and below is vulnerable to CSRF via Backend\File::approveVersion
Concrete CMS 9.5.0 and below is vulnerable to CSRF via Backend\File::approveVersion. Victim with editfilecontents permission is CSRF'd into publishing an attacker-chosen previously-uploaded version (downgrade to an older version of a file, or activation of a co-editor's unpublished version). The Concrete CMS security team gave this vulnerability a CVSS v.4.0 score of 2.3 with vector CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N. Thanks Winston Crooker for reporting.
Affected Software
Event History
Frequently Asked Questions
What is the severity of CVE-2026-8340?
CVE-2026-8340 has a risk score of 20, indicating high severity.
Is my Concrete CMS vulnerable if I'm using version 9.5.0 or below?
Yes, Concrete CMS versions 9.5.0 and below are vulnerable to CVE-2026-8340.
How do I fix CVE-2026-8340?
To fix CVE-2026-8340, upgrade to a version of Concrete CMS that is above 9.5.0.
What kind of attack does CVE-2026-8340 enable?
CVE-2026-8340 enables a Cross-Site Request Forgery (CSRF) attack allowing unauthorized file version approvals.
What permissions are required for exploitation of CVE-2026-8340?
The attacker must forge a request from a user with edit_file_contents permission to exploit CVE-2026-8340.