Concrete CMS up to 9.5.2 REST API Groups list endpoint Groups.php listGroups improper authorization

Summaryinfo

A vulnerability was found in Concrete CMS up to 9.5.2. It has been classified as problematic. This impacts the function listGroups of the file concrete/src/Api/Controller/Groups.php of the component REST API Groups list endpoint. Performing a manipulation results in improper authorization. This vulnerability is reported as CVE-2026-81908. The attack is possible to be carried out remotely. No exploit exists.

Detailsinfo

A vulnerability was found in Concrete CMS up to 9.5.2. It has been classified as problematic. This affects the function listGroups of the file concrete/src/Api/Controller/Groups.php of the component REST API Groups list endpoint. The manipulation with an unknown input leads to a improper authorization vulnerability. CWE is classifying the issue as CWE-285. The product does not perform or incorrectly performs an authorization check when an actor attempts to access a resource or perform an action. This is going to have an impact on confidentiality. The summary by CVE is:

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.

The advisory is shared at documentation.concretecms.org. This vulnerability is uniquely identified as CVE-2026-81908 since 08/27/2026. The exploitability is told to be easy. It is possible to initiate the attack remotely. Technical details are known, but no exploit is available. The price for an exploit might be around USD $0-$5k at the moment (estimation calculated on 09/11/2026). MITRE ATT&CK project uses the attack technique T1548.002 for this issue.

By approaching the search of inurl:concrete/src/Api/Controller/Groups.php it is possible to find vulnerable targets with Google Hacking.

There is no information about possible countermeasures known. It may be suggested to replace the affected object with an alternative product.

If you want to get the best quality for vulnerability data then you always have to consider VulDB.

Productinfo

Type

• Content Management System

Name

• Concrete CMS

Version

• 9.5.0
• 9.5.1
• 9.5.2

License

• open-source

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