{"dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": {"cveId": "CVE-2026-93628", "assignerOrgId": "9974b330-7714-4307-a722-5648477acda7", "state": "PUBLISHED", "assignerShortName": "rapid7", "dateReserved": "2026-09-18T12:22:34.911Z", "datePublished": "2026-10-23T13:18:16.368Z", "dateUpdated": "2026-10-23T13:18:16.368Z"}, "containers": {"cna": {"providerMetadata": {"orgId": "9974b330-7714-4307-a722-5648477acda7", "shortName": "rapid7", "dateUpdated": "2026-10-23T13:18:16.368Z"}, "title": "Zimbra Collaboration Suite Calendar Processing Authentication Bypass via Forged iCalendar REPLY Attendee Response", "datePublic": "2026-10-23T12:46:00.000Z", "problemTypes": [{"descriptions": [{"lang": "en", "cweId": "CWE-290", "description": "CWE-290 Authentication bypass by spoofing", "type": "CWE"}]}], "affected": [{"vendor": "Zimbra", "product": "Zimbra Collaboration Suite", "versions": [{"status": "affected", "version": "0", "lessThanOrEqual": "10.1.21", "versionType": "semver"}], "defaultStatus": "unaffected"}], "descriptions": [{"lang": "en", "value": "An attendee authentication vulnerability in the email calendar processing of Zimbra Collaboration Suite (ZCS) allows an unauthenticated sender to forge another attendee's response to an existing meeting. Zimbra passes a null sender identity when processing iCalendar REPLY components, causing the attendee authorization filter to be skipped. An attacker who knows the meeting UID, organizer address and attendee address can send a non-outdated reply that changes the attendee's participation status in the organizer's calendar. The change occurs automatically during delivery without organizer or attendee interaction. ZCS 10.1.16 and 10.1.21 are affected.", "supportingMedia": [{"type": "text/html", "base64": false, "value": "An attendee authentication vulnerability in the email calendar processing of Zimbra Collaboration Suite (ZCS) allows an unauthenticated sender to forge another attendee's response to an existing meeting. Zimbra passes a null sender identity when processing iCalendar REPLY components, causing the attendee authorization filter to be skipped. An attacker who knows the meeting UID, organizer address and attendee address can send a non-outdated reply that changes the attendee's participation status in the organizer's calendar. The change occurs automatically during delivery without organizer or attendee interaction. ZCS 10.1.16 and 10.1.21 are affected."}]}], "references": [{"url": "https://wiki.zimbra.com/wiki/Zimbra_Security_Advisories", "tags": ["vendor-advisory"]}, {"url": "https://www.rapid7.com/blog/post/ve-breaking-zimbra-identity-boundaries-part-1/", "tags": ["related"]}], "metrics": [{"format": "CVSS", "scenarios": [{"lang": "en", "value": "GENERAL"}], "cvssV3_1": {"version": "3.1", "attackVector": "NETWORK", "attackComplexity": "LOW", "privilegesRequired": "NONE", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "NONE", "integrityImpact": "LOW", "availabilityImpact": "NONE", "baseSeverity": "MEDIUM", "baseScore": 5.3, "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N"}}], "credits": [{"lang": "en", "value": "Jonah Burgess (CryptoCat), Senior Security Researcher, Rapid7", "type": "finder"}], "source": {"discovery": "UNKNOWN"}, "x_generator": {"engine": "Vulnogram 1.0.5"}}}}

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{"affected": [{"affectedData": [{"defaultStatus": "unaffected", "product": "Zimbra Collaboration Suite", "vendor": "Zimbra", "versions": [{"lessThanOrEqual": "10.1.21", "status": "affected", "version": "0", "versionType": "semver"}]}], "source": "cve@rapid7.com"}], "cveTags": [], "descriptions": [{"lang": "en", "value": "An attendee authentication vulnerability in the email calendar processing of Zimbra Collaboration Suite (ZCS) allows an unauthenticated sender to forge another attendee's response to an existing meeting. Zimbra passes a null sender identity when processing iCalendar REPLY components, causing the attendee authorization filter to be skipped. An attacker who knows the meeting UID, organizer address and attendee address can send a non-outdated reply that changes the attendee's participation status in the organizer's calendar. The change occurs automatically during delivery without organizer or attendee interaction. ZCS 10.1.16 and 10.1.21 are affected."}], "id": "CVE-2026-93628", "lastModified": "2026-10-23T14:17:56.667", "metrics": {"cvssMetricV31": [{"cvssData": {"attackComplexity": "LOW", "attackVector": "NETWORK", "availabilityImpact": "NONE", "baseScore": 5.3, "baseSeverity": "MEDIUM", "confidentialityImpact": "NONE", "integrityImpact": "LOW", "privilegesRequired": "NONE", "scope": "UNCHANGED", "userInteraction": "NONE", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N", "version": "3.1"}, "exploitabilityScore": 3.9, "impactScore": 1.4, "source": "cve@rapid7.com", "type": "Secondary"}]}, "published": "2026-10-23T14:17:56.667", "references": [{"source": "cve@rapid7.com", "url": "https://wiki.zimbra.com/wiki/Zimbra_Security_Advisories"}, {"source": "cve@rapid7.com", "url": "https://www.rapid7.com/blog/post/ve-breaking-zimbra-identity-boundaries-part-1/"}], "sourceIdentifier": "cve@rapid7.com", "vulnStatus": "Received", "weaknesses": [{"description": [{"lang": "en", "value": "CWE-290"}], "source": "cve@rapid7.com", "type": "Secondary"}]}

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