CVE-2026-87028

MEDIUM CVSS 4.0: 5.3 EPSS 0.38%
Updated Sep 21, 2026
Concretecms
Parameter Value
CVSS 5.3 (MEDIUM)
Affected Versions 9.0.0 — 9.5.3
Fixed In 9.5.3
Type CWE-862 (Missing Authorization)
Vendor Concretecms
Public PoC No

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.

Attack Parameters

Attack Vector
Network
Can be exploited remotely
Attack Complexity
Low
Easy to exploit
Attack Requirements
None
No additional conditions
Privileges Required
Low
Basic privileges needed
User Interaction
None
No user interaction needed

Impact Assessment

Confidentiality
Low
Partial data leak
Integrity
None
No data modification
Availability
None
No disruption

CVSS Vector v4.0

Vulnerable Products 1

Configuration From (including) Up to (excluding)
Concretecms Concrete_Cms
cpe:2.3:a:concretecms:concrete_cms:*:*:*:*:*:*:*:*
9.0.0 9.5.3