CVE-2026-8428

What it is

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.

At a glance

Exploitability

Can be exploited over the network without logging in, but needs a user to act. High risk of data exposure, data tampering, service disruption.

Exploit odds

0.1% chance of exploitation in the next 30 days (EPSS).

Fix

A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

1. 2026-05-21 21:16 UTC PublishedDisclosed publicly on CVE.org and NVD
2. 2026-07-23 16:10 UTC Last updatedMost recent change to the record

Details

Published

2026-05-21 21:16 UTC

Last modified

2026-07-23 16:10 UTC

Exploit probability

0.1% · EPSS, next 30 days

Weakness

CWE-352 · Cross-site request forgery

Record status

Analyzed

Affected

• Concretecms Concrete Cms < 9.5.1

Attack profile CVSS 4.0 · 7.5

Attack vector

Network

Complexity

High

Attack requirements

Present

Privileges needed

None

User interaction

Active

Confidentiality

High

Integrity

High

Availability

High