CVE-2026-8204 Details
Description
Concrete CMS 9.5.0 and below is vulnerable to authorization Bypass in the Calendar Event Frontend Dialog which can allow cross-calendar data disclosure. A public calendar block can be used as a pivot point to access private calendar data. The Concrete CMS security team gave this vulnerability a CVSS v.4.0 score of 6.3 with vector CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N. Thanks Winston Crooker for reporting.
An authorization bypass vulnerability has been identified in the Calendar Event Frontend Dialog of Concrete CMS versions through 9.5.0. This vulnerability can lead to unauthorized access to private calendar data by exploiting a public calendar block as a pivot point. The issue allows cross-calendar data disclosure, where private calendar information can be accessed through a publicly shared calendar.
Metrics
CVSS 4.0 Severity and Vector Strings:
CVSS 3.x Severity and Vector Strings:
No data available for CVSS Version 2.0 on this CVE.
CISA-ADP
Assessed May 22, 2026References to Advisories, Solutions, and Tools
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| URL | Source(s) | Tag(s) |
|---|---|---|
| https://documentation.concretecms.org/9-x/developers/introduction/version-history/951-release-notes | ConcreteCMS | Release Notes |
Weakness Enumeration
| CWE-ID | CWE Name | Source |
|---|---|---|
| CWE-639 | Authorization Bypass Through User-Controlled Key | ConcreteCMS |
Affected Products
| Product | Versions |
|---|---|
| concretecms concrete cms | < 9.5.1 |
CPE
Remediation
| |
Change History
5 change records found show changes
| Date | Action | Recorded By |
|---|---|---|
| Jul 23, 2026 | CVE Translated | [email protected] |
| Jun 17, 2026 | CVE Modified | ConcreteCMS |
| Jun 17, 2026 | CVE Modified | CISA-ADP |
| May 26, 2026 | Initial Analysis | [email protected] |
| May 21, 2026 | New CVE Received | ConcreteCMS |