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

23 Jul 2026, 16:10

Type	Values Removed	Values Added
Summary		(es) Concrete CMS 9.5.0 y versiones anteriores es vulnerable a una omisión de autorización en el Diálogo Frontend de Eventos del Calendario, lo que puede permitir la divulgación de datos entre calendarios. Un bloque de calendario público puede ser utilizado como punto de pivote para acceder a datos de calendario privados. El equipo de seguridad de Concrete CMS otorgó a esta vulnerabilidad una puntuación CVSS v.4.0 de 6.3 con el 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. Gracias a Winston Crooker por informar.

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 : 2026-07-23 16:10

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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