Missing authorization in Concrete CMS
Key facts
- Attack vector
- Network
- Privileges required
- High
- User interaction
- None
- Attack complexity
- Low
- Attack requirements
- Present
- Impact type
- Security bypass
- Confidentiality · integrity · availability
- None · Low · Low
- Fix status
- No fix listed
Attack profile from CVSS 4.0 · CNA. Fix status from CNA. Impact type from CWE-862.
Summary
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.
Why it matters now
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- None
- Automatable
- No
- Technical impact
- Partial
The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.
Affected products
No affected products listed by the sources yet.
CPE names Threatist (inferred) · 1
Inferred from how NVD named this product before; not given by a source.
| CPE | Versions | Role | Vendor |
|---|---|---|---|
| cpe:2.3:a:concretecms:concrete_cms:*:*:*:*:*:*:*:* | — | — | Concrete CMS |
- cpe:2.3:a:concretecms:concrete_cms:*:*:*:*:*:*:*:* Versions — — ·Concrete CMS
Remediation
No fixed version listed by the sources yet.
Timeline
- 2026-10-02 Threatist record created from CVE-2026-18421
- 2026-10-03 Alias added: GHSA-266p-gm36-gqvf
References
More Concrete CMS vulnerabilities
- TI-2026-23602 ConcreteCMS v9.4.7 contains a Denial of Service (DoS) vulnerability in the File Manager… CVSS 3.1MEDIUM 6.5
- TI-2023-23992 A Cross Site Scripting (XSS) vulnerability in Concrete CMS from versions 9.2.0 to 9.2.2… CVSS 3.1MEDIUM 5.4
- TI-2023-26495 Concrete CMS before 8.5.13 and 9.x before 9.2.2 allows unauthorized access because… CVSS 3.1CRITICAL 9.8
- TI-2026-14907 Missing authorization in Concrete CMS CVSS 4.0HIGH 8.7
- TI-2022-06200 Cleartext transmission of sensitive information in https://github.com/concrete5/concrete5 CVSS 3.1CRITICAL 9.8
- TI-2021-17294 An issue was discovered in Concrete CMS through 8.5.5. CVSS 3.1CRITICAL 9.8
Sources
- CVE-2026-18421 · CVE Program
- CVE-2026-18421 · NVD
- FIRST EPSS
- GHSA-266p-gm36-gqvf · GitHub Advisory Database · CC BY 4.0
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