# CVE-2026-81902: Concrete CMS CSRF token validation bypass in block removal

Source: https://junglewise.ai/threats/cve-2026-81902-concrete-cms-csrf-token-validation-bypass-in-block-removal  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-09-14. Updated: 2026-09-26  
License: CC BY 4.0 with a link back

CVE-2026-81902 · Severity: high · CVSS 8.1 · Published 2026-09-14

Concrete CMS is a web content management system used to build and manage websites. A missing security check (CSRF token validation) in the orphaned block removal feature allows an attacker to craft a malicious request that, when visited by an authenticated editor, permanently deletes all blocks and associated content on a page. This results in irreversible data loss and potential service disruption.

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

## Quick answers

**Is CVE-2026-81902 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-81902 being exploited in the wild.

**How severe is CVE-2026-81902?** High severity, with a CVSS score of 8.1, published 14 September 2026.

**Which products and versions are affected?** Concrete CMS 9 through 9.5.2.

**Is there a fix for CVE-2026-81902?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2026-81902 attacked?** It is attacked over the network, in a web application.

**Am I affected by CVE-2026-81902?** Check whether you run Concrete CMS 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.

## Technical details

The vulnerability is a Cross-Site Request Forgery (CSRF) token validation bypass in the removeOrphanedBlocks panel action. Concrete CMS 9 through 9.5.2 fail to properly validate anti-CSRF tokens before processing the orphaned block removal request. An unauthenticated attacker can craft a malicious request that, when executed in the browser context of an authenticated user with edit permissions on a target page, triggers deletion of all blocks on that page's current version. Blocks that are not aliased to other pages or scrapbook entries are also permanently removed from the global Blocks table and their corresponding block-type data tables. No patches are mentioned in the advisory as available at the time of publication.

## Affected products

- Concrete CMS Concrete CMS 9 through 9.5.2

## Timeline

- 2026-09-14: disclosed

## References

- [https://github.com/concretecms/concretecms](https://github.com/concretecms/concretecms)
- [https://documentation.concretecms.org/developers/introduction/version-history/953-release-notes](https://documentation.concretecms.org/developers/introduction/version-history/953-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)