Vulnerability · Published Sep 10, 2026 · Assigned by ConcreteCMS
CVE-2026-68527Concrete CMS 8.3.0 through 9.5.2 is vulnerable to an authorization bypass through user-controlled key (cross-calendar IDOR) in the Calendar event edit dialog
Medium 5.9
In plain English
A medium-severity authorization bypass via user-controlled key in Concrete CMS from Concrete CMS. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.5% (higher than 41% of all known vulnerabilities).
Official description
Concrete CMS versions 8.3.0 through 9.5.2 are vulnerable to an authorization bypass in the Calendar event edit dialog (concrete/controllers/dialog/event/edit.php). The dialog checked permissions against the calendar identifier supplied in the request rather than the calendar owning the targeted event occurrence. A user with the "Add Event" permission on a single calendar could read and overwrite events on calendars they were not permitted to access, and could delete an event's original local occurrence. Publishing the injected version to the live calendar, which demotes the previously approved version, additionally required the actor's approve_calendar_event workflow rights or an auto-approving workflow. The Concrete CMS Security Team gave this a rank of 5.9 with CVSS 4.0 vector CVSS:4.0/AV:N/AC:L/AT:P/PR:H/UI:N/VC:L/VI:H/VA:L/SC:N/SI:N/SA:N. Thanks Winston Crooker for reporting.
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| Concrete CMS | Concrete CMS | 8.3.0 – through 9.5.2 |
Weakness: CWE-639 · Vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:H/UI:N/VC:L/VI:H/VA:L/SC:N/SI:N/SA:N