{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-8204","assignerOrgId":"ff5b8ace-8b95-4078-9743-eac1ca5451de","state":"PUBLISHED","assignerShortName":"ConcreteCMS","dateReserved":"2026-05-09T00:11:45.659Z","datePublished":"2026-05-21T20:56:33.018Z","dateUpdated":"2026-05-22T12:27:38.540Z"},"containers":{"cna":{"providerMetadata":{"orgId":"ff5b8ace-8b95-4078-9743-eac1ca5451de","shortName":"ConcreteCMS","dateUpdated":"2026-05-21T20:56:33.018Z"},"title":"Concrete CMS 9.5.0 and below is vulnerable to Authorization Bypass in the Calendar Event Frontend Dialog","problemTypes":[{"descriptions":[{"lang":"en","cweId":"CWE-639","description":"CWE-639 Authorization bypass through User-Controlled key","type":"CWE"}]}],"impacts":[{"capecId":"CAPEC-116","descriptions":[{"lang":"en","value":"CAPEC-116 Excavation"}]}],"affected":[{"vendor":"Concrete CMS","product":"Concrete CMS","collectionURL":"https://github.com/concretecms/concretecms","repo":"https://github.com/concretecms/concretecms","versions":[{"status":"affected","version":"5","lessThanOrEqual":"9.5.0","versionType":"git"}],"defaultStatus":"unaffected"}],"descriptions":[{"lang":"en","value":"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.","supportingMedia":[{"type":"text/html","base64":false,"value":"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&nbsp;6.3 with vector&nbsp;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&nbsp;Winston Crooker for reporting.&nbsp;"}]}],"references":[{"url":"https://documentation.concretecms.org/9-x/developers/introduction/version-history/951-release-notes","tags":["release-notes"]}],"metrics":[{"format":"CVSS","scenarios":[{"lang":"en","value":"GENERAL"}],"cvssV4_0":{"attackVector":"NETWORK","attackComplexity":"LOW","attackRequirements":"PRESENT","privilegesRequired":"NONE","userInteraction":"NONE","vulnConfidentialityImpact":"LOW","subConfidentialityImpact":"NONE","vulnIntegrityImpact":"NONE","subIntegrityImpact":"NONE","vulnAvailabilityImpact":"NONE","subAvailabilityImpact":"NONE","exploitMaturity":"NOT_DEFINED","Safety":"NOT_DEFINED","Automatable":"NOT_DEFINED","Recovery":"NOT_DEFINED","valueDensity":"NOT_DEFINED","vulnerabilityResponseEffort":"NOT_DEFINED","providerUrgency":"NOT_DEFINED","version":"4.0","baseSeverity":"MEDIUM","baseScore":6.3,"vectorString":"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"}}],"credits":[{"lang":"en","value":"Winston Crooker","type":"finder"}],"source":{"defect":["HackerOne"],"advisory":"https://hackerone.com/reports/3641132","discovery":"EXTERNAL"},"x_generator":{"engine":"Vulnogram 1.0.2"}},"adp":[{"metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2026-05-22T12:27:29.187587Z","id":"CVE-2026-8204","options":[{"Exploitation":"none"},{"Automatable":"no"},{"Technical Impact":"partial"}],"role":"CISA Coordinator","version":"2.0.3"}}}],"title":"CISA ADP Vulnrichment","providerMetadata":{"orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","shortName":"CISA-ADP","dateUpdated":"2026-05-22T12:27:38.540Z"}}]}}