CVE-2026-18421

Received Received - Intake

Authorization Bypass in ConfiguredDataSource in Concrete CMS

Publication date: 2026-09-15

Last updated on: 2026-09-15

Assigner: ConcreteCMS

Description

Concrete CMS 9 through 9.5.2 does not perform an authorization check in three actions of the Boards data source dashboard controller (update, update_data_source, and delete_data_source), which resolve a ConfiguredDataSource directly from an attacker-supplied identifier without confirming the requester's edit permission on the owning board. A user granted edit_board_settings on a single board was therefore able to modify or permanently delete the configured data sources of any other board on the site, halting the affected board's content feed and resetting its custom weighting. The CSRF token that guards these actions was validated but bound to the action name rather than to the target object, so a token legitimately obtained for one board could be replayed against another board's ConfiguredDataSource identifier and did not constrain access. The Concrete CMS security team gave this vulnerability a CVSS v4.0 score of 2.1 with vector CVSS:4.0/AV:N/AC:L/AT:P/PR:H/UI:N/VC:N/VI:L/VA:L/SC:N/SI:N/SA:N. Thanks Winston Crooker for reporting.

CVSS Scores

EPSS Scores

Probability:
Percentile:

Meta Information

Published

2026-09-15

Last Modified

2026-09-15

Generated

2026-10-06

AI Q&A

2026-09-16

EPSS Evaluated

2026-10-04

NVD

CVE-2026-18421

EUVD

EUVD-2026-79187

Affected Vendors & Products

Vendor	Product	Version / Range
concrete_cms	concrete_cms	From 9 (inc) to 9.5.2 (inc)

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-862	The product does not perform an authorization check when an actor attempts to access a resource or perform an action.

Attack-Flow Graph

Executive Summary

Concrete CMS versions 9 through 9.5.2 have a flaw in the Boards data source dashboard controller. The system fails to verify if a user has permission to edit a specific board before allowing actions like updating or deleting its data sources. This means a user with edit rights on one board can modify or delete data sources of any other board, disrupting content feeds and resetting custom settings.

Detection Guidance

This vulnerability affects Concrete CMS versions 9 through 9.5.2. To detect it, check for unauthorized modifications to data sources in the Boards dashboard. Review logs for actions like update, update_data_source, or delete_data_source on ConfiguredDataSource objects. Verify if users with edit_board_settings on one board can alter data sources of other boards.

Impact Analysis

If you use Concrete CMS with multiple boards, an attacker with limited access could disrupt other boards' content feeds or delete their data sources. This could lead to downtime, loss of custom configurations, or unauthorized changes to board data.

Compliance Impact

This vulnerability does not directly impact GDPR or HIPAA compliance as it involves unauthorized modification or deletion of data sources in Concrete CMS, which is a content management system issue rather than a data privacy or health information breach. However, unauthorized changes to data feeds could indirectly affect compliance by disrupting data integrity or availability.

Mitigation Strategies

Update Concrete CMS to a version beyond 9.5.2 where the authorization check vulnerability has been fixed. Review user permissions to ensure only authorized users have edit_board_settings access. Monitor data source configurations for unauthorized changes.

Hi! I’m here to help you understand CVE-2026-18421. Ask me anything about the vulnerability, its impact, or mitigation strategies.

0/70