CVE-2026-8204

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.

CVSS v3 5.3 MEDIUM

5.3^/10

CVSS v3 : MEDIUM

Vector :

Exploitability : 3.9 / Impact : 1.4

Attack Vector NETWORK

Attack Complexity LOW

Privileges Required NONE

User Interaction NONE

Confidentiality Impact LOW

Integrity Impact NONE

Availability Impact NONE

Scope UNCHANGED

References

Link	Resource
https://documentation.concretecms.org/9-x/developers/introduction/version-history/951-release-notes	Release Notes

Configurations

Configuration 1 (hide)

cpe:2.3:a:concretecms:concrete_cms:*:*:*:*:*:*:*:*

History

26 May 2026, 14:58

Type	Values Removed	Values Added
CVSS	v2 : ~~unknown~~ v3 : ~~unknown~~	v2 : unknown v3 : 5.3
First Time		Concretecms concrete Cms Concretecms
References	~~() https://documentation.concretecms.org/9-x/developers/introduction/version-history/951-release-notes -~~	() https://documentation.concretecms.org/9-x/developers/introduction/version-history/951-release-notes - Release Notes
CPE		cpe:2.3:a:concretecms:concrete_cms::::::::

21 May 2026, 21:16

Type	Values Removed	Values Added
New CVE

Information

Published : 2026-05-21 21:16

Updated : 2026-05-26 14:58

NVD link : CVE-2026-8204

Mitre link : CVE-2026-8204

CVE.ORG link : CVE-2026-8204

JSON object : View

Products Affected

concretecms

concrete_cms

CWE

CWE-639

Authorization Bypass Through User-Controlled Key

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