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CVE-2026-87028

Concrete CMS · Vulnerability

CVSS 4.0 5.3 MEDIUMCheck source for fixed versionsKEV status unknown

Original advisory

cve-program · CVE-2026-87028

Published

Concrete CMS 9 through 9.5.3 did not confirm that a board InstanceItem submitted to the custom-slot preview endpoint belonged to the board instance the requesting user was authorized to edit, and did not enforce page-view permission before generating page-backed summary content. As a result, an authenticated user holding edit-board-contents permission on a single board instance could submit the identifier of an item belonging to a different board instance and receive summary fields, including the page title and description, of an underlying page the same user was otherwise forbidden to view. The Concrete CMS security team gave this vulnerability a CVSS v4.0 score of 5.3 with vector CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N. Thanks Pakung for reporting.

Read the publisher's advisory

Affected versions, risk and source history

cve-program · CVE-2026-87028

Published

Concrete CMS

https://github.com/concretecms/concretecms

Publisher's version information

Shown as published. These rules are not interpreted as NuGet package version ranges.

{
                    "vendor": "Concrete CMS",
                    "product": "Concrete CMS",
                    "collectionURL": "https://github.com/concretecms/concretecms",
                    "repo": "https://github.com/concretecms/concretecms",
                    "versions": [
                        {
                            "status": "affected",
                            "version": "9.0.0",
                            "lessThanOrEqual": "9.5.3",
                            "versionType": "git"
                        }
                    ],
                    "defaultStatus": "unaffected"
                }

Original source record · Cite this exact observation · Complete original publisher JSON