Concrete CMS up to 9.5.0 local_available_update.php do_update token cross-site request forgery

Summaryinfo

A vulnerability classified as problematic has been found in Concrete CMS up to 9.5.0. Affected by this issue is the function do_update of the file local_available_update.php. Performing a manipulation of the argument token results in cross-site request forgery. This vulnerability is identified as CVE-2026-8428. The attack can be initiated remotely. There is not any exploit available.

Detailsinfo

A vulnerability was found in Concrete CMS up to 9.5.0. It has been classified as problematic. This affects the function do_update of the file local_available_update.php. The manipulation of the argument token with an unknown input leads to a cross-site request forgery vulnerability. CWE is classifying the issue as CWE-352. The web application does not, or can not, sufficiently verify whether a well-formed, valid, consistent request was intentionally provided by the user who submitted the request. This is going to have an impact on integrity. The summary by CVE 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.

It is possible to read the advisory at documentation.concretecms.org. This vulnerability is uniquely identified as CVE-2026-8428 since 05/12/2026. The exploitability is told to be easy. It is possible to initiate the attack remotely. No form of authentication is needed for exploitation. It demands that the victim is doing some kind of user interaction. Technical details of the vulnerability are known, but there is no available exploit.

By approaching the search of inurl:local_available_update.php it is possible to find vulnerable targets with Google Hacking.

There is no information about possible countermeasures known. It may be suggested to replace the affected object with an alternative product.

The vulnerability is also documented in the vulnerability database at EUVD (EUVD-2026-31340). Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.

Productinfo

Type

• Content Management System

Vendor

• Concrete

Name

• CMS

Version

• 9.0
• 9.1
• 9.2
• 9.3
• 9.4
• 9.5.0

License

• open-source

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Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.

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