Concrete CMS up to 9.5.2 Autocomplete Endpoint autocomplete improper authorization

Summaryinfo

A vulnerability was found in Concrete CMS up to 9.5.2. It has been rated as problematic. This impacts an unknown function of the file /ccm/system/user/autocomplete of the component Autocomplete Endpoint. The manipulation leads to improper authorization. This vulnerability is traded as CVE-2026-18110. It is possible to initiate the attack remotely. There is no exploit available.

Detailsinfo

A vulnerability was found in Concrete CMS up to 9.5.2. It has been rated as problematic. This issue affects an unknown function of the file /ccm/system/user/autocomplete of the component Autocomplete Endpoint. The manipulation with an unknown input leads to a improper authorization vulnerability. Using CWE to declare the problem leads to 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. Impacted is confidentiality. The summary by CVE is:

Concrete CMS 9 (9.0.0 through 9.5.2) does not perform an authorization check on the user selector autocomplete endpoint (/ccm/system/user/autocomplete), which backs the "Preview as User" panel and other user-selector components. The endpoint validates only a CSRF-style access token that is bound to the selector's display options rather than to the caller's identity or permissions, and that token is issued to anonymous visitors because the selector renders without an authorization check. Because an empty query resolves to a match-all filter, an unauthenticated attacker can submit an empty search and paginate the results to enumerate every backend account, disclosing the internal user ID, username, and email address of all administrative users, including the super-administrator (user ID 1). No password hashes or session material are disclosed The Concrete CMS security team gave this vulnerability a CVSS v4.0 score of 8.7 with vector CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N. Thanks thirtythree and YesWeHack for reporting.

The advisory is shared at documentation.concretecms.org. The identification of this vulnerability is CVE-2026-18110 since 07/28/2026. The exploitation is known to be easy. The attack may be initiated remotely. No form of authentication is needed for a successful exploitation. 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 09/15/2026). MITRE ATT&CK project uses the attack technique T1548.002 for this issue.

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

Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

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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Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

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