CVE-2026-18122: Concrete CMS 9.2.0 to 9.5.2 Express REST API list endpoint exposes restricted Express entries via Missing Authorization
Concrete CMS 9.2.0 to 9.5.2 Express REST API list endpoint exposes restricted Express entries via Missing Authorization; the Concrete CMS REST API's Express entry collection endpoint disabled the per-entry view permission check. An OAuth token with read scope for an Express entity could enumerate entries that its user context lacked permission to view, disclosing each entry's public identifier, URL, label, dates, and any attribute or associated-entry data requested via the includes parameter. 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 riodrwn for reporting.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
Concrete CMS Express REST APIto a version that resolves this vulnerability.Fixed in 9.5.2 - Configuration
Enable the per-entry view permission check for the Express entry collection endpoint to prevent OAuth tokens with read scope from enumerating restricted Express entries via the list endpoint.
Concrete CMS REST API (Express entry collection endpoint) per-entry view permission check = enabled
Event History
Frequently Asked Questions
Who can exploit this issue?
An attacker needs an OAuth token with read scope for the affected Express entity. The token's user context does not need permission to view the individual entries that can be enumerated.
What information can be exposed?
The endpoint can disclose each restricted entry's public identifier, URL, label, and dates. It can also disclose attribute or associated-entry data when that data is requested through the includes parameter.
Which deployments are affected?
Concrete CMS versions 9.2.0 through 9.5.2 are affected. Exposure is relevant where the REST API Express entry collection endpoint is available and OAuth tokens have read scope for an Express entity.