2.3

CVSS Score

4.0

-

CVSS Score

Basic Information

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CVE-2026-8340

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 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an attacker-chosen previously-uploaded version (downgrade to an older version of a file, or activation of a co-editor's unpublished version).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.

(GitHub Advisory)

Miggo Vulnerability Database

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CVE-2026-8340

CVE-2026-8340:

2.3

CVSS Score

4.0

-

CVSS Score

Basic Information

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Technical Details

SSVC / BOD 26-04 ↗

Exploitation NoneAutomatable NoTech Impact Partial

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Package Name	Ecosystem	Vulnerable Versions	First Patched Version
concrete5/concrete5	composer	< 9.5.1	9.5.1

Technical Details

Vulnerability Intelligence
Miggo AI

Root Cause Analysis

The vulnerability described is a Cross-Site Request Forgery (CSRF) in the Backend\File::approveVersion method of Concrete CMS. By analyzing the commits between the vulnerable version (9.5.0) and the patched version (9.5.1), I identified a security-related commit f22b9dff59454391a50a255a39995bf635deea9e with the message "Sec fixes 9.5.1". Within this commit, the file concrete/controllers/backend/file.php was modified. Specifically, the approveVersion function had a CSRF token validation check added. The absence of this check in the vulnerable versions allowed attackers to perform CSRF attacks. Therefore, the vulnerable function is Concrete\Controller\Backend\File::approveVersion.

Vulnerable functions

Concrete\Controller\Backend\File::approveVersion

concrete/controllers/backend/file.php

The `approveVersion` function in `concrete/controllers/backend/file.php` was missing a CSRF token validation. This allowed an attacker to trick a victim with `edit_file_contents` permission into approving a specific version of a file without their consent, by crafting a malicious request. The patch adds a token validation to ensure that the request is legitimate and originates from the user.

Vulnerability Intelligence
Miggo AI

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WAF Protection Rules

WAF Rule

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Reasoning

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