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CVE-2026-8340— Concrete CMS 9.5.0 and below is vulnerable to CSRF via Backend\File::approveVersion

Quick assessment

Affected
Concrete CMS Concrete CMS
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Concrete CMS是Concrete CMS开源的一个面向团队的开源内容管理系统。 Concrete CMS 9.5.0及之前版本存在安全漏洞，该漏洞源于容易受到跨站请求伪造攻击，可能导致具有edit_file_contents权限的受害者被跨站请求伪造攻击，从而发布攻击者选择的先前上传的版本。

AI Predicted 6.5 Difficulty: Easy EPSS 0.15% · P3

Possible ATT&CK Techniques 1 AI

T1190 · Exploit Public-Facing Application

Affected Version Matrix 1

VendorProduct Version RangeStatus
Concrete CMS Concrete CMS 5.0≤ 9.5.0 affected
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I. Basic Information for CVE-2026-8340

Vulnerability Information
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Vulnerability Title
Concrete CMS 9.5.0 and below is vulnerable to CSRF via Backend\File::approveVersion
Source: CVE Program / CVE List V5
Vulnerability Description
Concrete CMS 9.5.0 and below is vulnerable to CSRF via Backend\File::approveVersion. Victim with edit_file_contents 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an attacker-chosen previously-uploaded version (downgrade to an older version of a file, or activation of a co-editor's unpublished version).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.
Source: CVE Program / CVE List V5
CVSS Information
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
Source: CVE Program / CVE List V5
Vulnerability Type
跨站请求伪造(CSRF)
Source: CVE Program / CVE List V5
Vulnerability Title
Concrete CMS 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Concrete CMS是Concrete CMS开源的一个面向团队的开源内容管理系统。 Concrete CMS 9.5.0及之前版本存在安全漏洞，该漏洞源于容易受到跨站请求伪造攻击，可能导致具有edit_file_contents权限的受害者被跨站请求伪造攻击，从而发布攻击者选择的先前上传的版本。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
Concrete CMS Concrete CMS 5.0 ~ 9.5.0 -

II. Public POCs for CVE-2026-8340

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III. Intelligence Information for CVE-2026-8340

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Vendor Pages for CVE-2026-8340 (1)

Same Patch Batch · Concrete CMS · 2026-05-22 · 3 CVEs total

CVE-2026-8347 Concrete CMS 9.5.0 and below is vulnerable to IDOR + wrong-authorization-level in Express
CVE-2026-8353 Concrete CMS version 9.0 to 9.5.0 is vulnerable to Stored XSS via page name in atomik them

IV. Related Vulnerabilities

Same product: Concrete CMS
Same vendor: Concrete CMS
Same weakness: CWE-352

V. Comments for CVE-2026-8340

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