CVE-2026-81908 Missing authorization in Concrete CMS
Authenticated users can enumerate all site groups via the REST API, exposing organizational structure and roles.
- 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-2026-81908?
CVE-2026-81908 is a medium-severity missing authorization vulnerability in Concrete CMS, published on 11 Sep 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Official description
Concrete CMS 9.2.0 to 9.5.2 contain a missing authorization vulnerability in the REST API Groups list endpoint. The listGroups() method in concrete/src/Api/Controller/Groups.php registers a permissions checker callback that unconditionally returns true, so no per-object (tree node) authorization is enforced when the group collection is returned. An authenticated user whose API token carries the groups:read scope can call GET /ccm/api/1.0/groups and receive every group on the site regardless of the view permissions on those groups, disclosing the organization's group structure, roles, and access hierarchy. The Concrete CMS security team gave this vulnerability a CVSS v4.0 score of 6.0 with vector CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N. Thanks Winston Crooker for reporting.
Weakness: CWE-862
Which versions are affected by CVE-2026-81908?
How do I fix CVE-2026-81908?
No fix has been published for CVE-2026-81908 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-2026-81908 being exploited?
There is no known exploitation of CVE-2026-81908 in the wild and no public exploit code.
Sources
Also known as GHSA-865j-87f7-7r6w.