# CVE-2026-8435: Concrete CMS CSRF in file version approval

Source: https://junglewise.ai/threats/cve-2026-8435-concrete-cms-csrf-in-file-version-approval  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-05-21. Updated: 2026-06-24  
License: CC BY 4.0 with a link back

CVE-2026-8435 · Severity: medium · CVSS 4 · Published 2026-05-21

Concrete CMS, a content management system used for building websites, is vulnerable to a security flaw that could allow an attacker to trick an administrator into performing unintended actions. Specifically, an attacker could cause a user with the appropriate permissions to approve a file version without their knowledge. This requires the attacker to successfully lure a logged-in administrator to a malicious website or link.

Technologies: [Concrete CMS](https://junglewise.ai/threats/technologies/concrete-cms), [concrete5/concrete5 (Packagist)](https://junglewise.ai/threats/technologies/concrete5-concrete5). Vendors: [Concrete CMS](https://junglewise.ai/threats/vendors/concrete-cms), [Packagist](https://junglewise.ai/threats/vendors/packagist).

## Quick answers

**Is CVE-2026-8435 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-8435 being exploited in the wild.

**How severe is CVE-2026-8435?** Medium severity, with a CVSS score of 4, published 21 May 2026.

**Which products and versions are affected?** Concrete CMS >= 9.0.0RC1, < 9.5.1; concrete5/concrete5 (Packagist) >= 9.0.0RC1, < 9.5.1, ECOSYSTEM:introduced=9.0.0RC1,fixed=9.5.1.

**Is there a fix for CVE-2026-8435?** Yes. concrete5/concrete5 (Packagist): upgrade to 9.5.1 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-8435 attacked?** It is attacked over the network, in a network appliance.

**Am I affected by CVE-2026-8435?** Check whether you run Concrete CMS or concrete5/concrete5 (Packagist) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- concrete5/concrete5 (Packagist): upgrade to 9.5.1 or later

  ```sh
  composer require concrete5/concrete5:^9.5.1
  ```


## Technical details

A Cross-Site Request Forgery (CSRF) vulnerability exists in Concrete CMS versions 9.0.0RC1 through 9.5.0. The flaw is located in the `approveVersion()` method within the `concrete/controllers/backend/file` controller. The application fails to properly validate CSRF tokens or implement sufficient SameSite cookie attributes for this specific endpoint. An attacker can exploit this by crafting a malicious webpage that, when visited by an authenticated administrator, triggers a background request to approve a specific file version. This could be used to bypass content review workflows. The issue is resolved in version 9.5.1.

## Affected products

- Concrete CMS Concrete CMS >= 9.0.0RC1, < 9.5.1

## Identifiers

- CVE-2026-8435
- GHSA-44q4-354f-c826

## Timeline

- 2026-05-21: disclosed: NVD publication date
- 2026-05-22: advisory: GitHub Advisory published
- 2026-06-24: patched: Advisory updated with patch information

## References

- [https://documentation.concretecms.org/9-x/developers/introduction/version-history/951-release-notes](https://documentation.concretecms.org/9-x/developers/introduction/version-history/951-release-notes)

## Related threats

- [Concrete CMS OAuth REST API authorization bypass](https://junglewise.ai/threats/cve-2026-85387-concrete-cms-oauth-rest-api-authorization-bypass)
- [Concrete CMS unauthenticated Express entry search disclosure](https://junglewise.ai/threats/cve-2026-18120-concrete-cms-unauthenticated-express-entry-search-disclosure)
- [Concrete CMS REST API user creation permission bypass](https://junglewise.ai/threats/cve-2026-87031-concrete-cms-rest-api-user-creation-permission-bypass)
- [Concrete CMS access control bypass in board custom-slot preview](https://junglewise.ai/threats/cve-2026-87028-concrete-cms-access-control-bypass-in-board-custom-slot-preview)
- [Concrete CMS stored XSS via XML file upload in Form Block](https://junglewise.ai/threats/cve-2026-85386-concrete-cms-stored-xss-via-xml-file-upload-in-form-block)