CVE-2026-8204

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.

PUBLISHED Reserved 2026-05-09 | Published 2026-05-21 | Updated 2026-05-21 | Assigner ConcreteCMS

Problem types

CWE-639 Authorization bypass through User-Controlled key

Product status

Credits

Winston Crooker finder

References

documentation.concretecms.org/...n-history/951-release-notes release-notes

cve.org (CVE-2026-8204)

nvd.nist.gov (CVE-2026-8204)

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