CVE-2026-8204
Analyzed Analyzed - Analysis Complete
Authorization Bypass in Concrete CMS Calendar Event Dialog

Publication date: 2026-05-21

Last updated on: 2026-05-26

Assigner: ConcreteCMS

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.
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Meta Information
Published
2026-05-21
Last Modified
2026-05-26
Generated
2026-06-12
AI Q&A
2026-05-22
EPSS Evaluated
2026-06-10
NVD
CVE-2026-8204
Affected Vendors & Products
Showing 1 associated CPE
Vendor Product Version / Range
concretecms concrete_cms to 9.5.1 (exc)
Helpful Resources
Exploitability
CWE
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KEV
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CWE ID Description
CWE-639 The system's authorization functionality does not prevent one user from gaining access to another user's data or record by modifying the key value identifying the data.
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Executive Summary

This vulnerability affects Concrete CMS version 9.5.0 and below. It is an authorization bypass issue in the Calendar Event Frontend Dialog. Specifically, it allows an attacker to use a public calendar block as a pivot point to access private calendar data, leading to cross-calendar data disclosure.

Impact Analysis

The impact of this vulnerability is that unauthorized users can gain access to private calendar data by exploiting the authorization bypass. This could lead to exposure of sensitive or confidential information that was intended to be private.

Compliance Impact

The vulnerability in Concrete CMS 9.5.0 and below allows unauthorized access to private calendar data through a public calendar block, leading to cross-calendar data disclosure.

Such unauthorized data disclosure could potentially impact compliance with data protection regulations like GDPR and HIPAA, which require strict controls over access to personal and sensitive information.

However, the provided information does not explicitly detail the compliance implications or specific regulatory impacts of this vulnerability.

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