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.
History

Tue, 26 May 2026 15:00:00 +0000

Type Values Removed Values Added
CPEs cpe:2.3:a:concretecms:concrete_cms:*:*:*:*:*:*:*:*
Metrics cvssV3_1

{'score': 5.3, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N'}


Fri, 22 May 2026 13:30:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}


Thu, 21 May 2026 23:30:00 +0000

Type Values Removed Values Added
First Time appeared Concretecms
Concretecms concrete Cms
Vendors & Products Concretecms
Concretecms concrete Cms

Thu, 21 May 2026 21:00:00 +0000

Type Values Removed Values Added
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.
Title Concrete CMS 9.5.0 and below is vulnerable to Authorization Bypass in the Calendar Event Frontend Dialog
Weaknesses CWE-639
References
Metrics cvssV4_0

{'score': 6.3, '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'}


cve-icon MITRE

Status: PUBLISHED

Assigner: ConcreteCMS

Published: 2026-05-21T20:56:33.018Z

Updated: 2026-05-22T12:27:38.540Z

Reserved: 2026-05-09T00:11:45.659Z

Link: CVE-2026-8204

cve-icon Vulnrichment

Updated: 2026-05-22T12:27:34.914Z

cve-icon NVD

Status : Analyzed

Published: 2026-05-21T21:16:33.530

Modified: 2026-05-26T14:58:25.500

Link: CVE-2026-8204

cve-icon Redhat

No data.