CVE-2026-87028 Missing authorization in Concrete CMS
Authenticated users can view restricted page summaries from unauthorized boards due to missing authorization checks in the custom slot preview endpoint.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-87028?
CVE-2026-87028 is a medium-severity missing authorization vulnerability in Concretecms Concrete Cms, published on 16 Sep 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Official description
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.
Weakness: CWE-862
Which versions are affected by CVE-2026-87028?
It affects 1 product.
Products include Concretecms Concrete Cms.
How do I fix CVE-2026-87028?
No fix has been published for CVE-2026-87028 yet. Limit exposure of the affected software until one is available.
Upgrade, and check permissions on every request on the server, not only in the interface. More about Missing authorization.
Is CVE-2026-87028 being exploited?
There is no known exploitation of CVE-2026-87028 in the wild and no public exploit code.
Other vulnerabilities in Concretecms Concrete Cms
- CVE-2023-48648 Concrete CMS allows unauthorized access because directories can be created with insecure permissions
- CVE-2022-21829 Code injection in concrete CMS
- CVE-2021-22958 Server-Side Request Forgery vulnerability in concrete5
- CVE-2021-40098 Path traversal in n/a
- CVE-2026-8134 Concrete CMS Vulnerable to Relative Path Traversal
Sources
Also known as GHSA-3qqv-7xrx-4vm6.