{"id":"CVE-2026-93628","state":"PUBLISHED","title":"Zimbra Collaboration Suite Calendar Processing Authentication Bypass via Forged iCalendar REPLY Attendee Response","description":"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 An attacker who knows the meeting UID, organizer address and attendee address can send a non-outdated reply that changes the attendee's participation status in the organizer's calendar.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.","publishedAt":"2026-10-23T13:18:16.368Z","updatedAt":"2026-10-28T20:02:01.885Z","severity":{"score":5.3,"label":"Medium","version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N","source":"rapid7"},"assigner":"rapid7","products":["Zimbra Zimbra Collaboration Suite"],"affected":[{"vendor":"Zimbra","product":"Zimbra Collaboration Suite","defaultStatus":"unaffected","versions":[{"version":"0","status":"affected","lessThanOrEqual":"10.1.21","versionType":"semver"}]}],"references":["https://wiki.zimbra.com/wiki/Zimbra_Security_Advisories","https://www.rapid7.com/blog/post/ve-breaking-zimbra-identity-boundaries-part-1/"],"weaknesses":["CWE-290"],"ingestedAt":"2026-10-29T20:13:34.582Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/93xxx/CVE-2026-93628.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-93628","state":"PUBLISHED","datePublished":"2026-10-23T13:18:16.368Z","dateUpdated":"2026-10-28T20:02:01.885Z","assignerShortName":"rapid7","assignerOrgId":"9974b330-7714-4307-a722-5648477acda7","dateReserved":"2026-09-18T12:22:34.911Z"},"containers":{"cna":{"title":"Zimbra Collaboration Suite Calendar Processing Authentication Bypass via Forged iCalendar REPLY Attendee Response","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."}],"affected":[{"vendor":"Zimbra","product":"Zimbra Collaboration Suite","defaultStatus":"unaffected","versions":[{"version":"0","status":"affected","lessThanOrEqual":"10.1.21","versionType":"semver"}]}],"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"}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-290","lang":"en","description":"CWE-290 Authentication bypass by spoofing","type":"CWE"}]}],"providerMetadata":{"shortName":"rapid7","orgId":"9974b330-7714-4307-a722-5648477acda7","dateUpdated":"2026-10-23T13:18:16.368Z"},"datePublic":"2026-10-23T12:46:00.000Z","credits":[{"lang":"en","value":"Jonah Burgess (CryptoCat), Senior Security Researcher, Rapid7","type":"finder"}],"source":{"discovery":"UNKNOWN"},"x_generator":{"engine":"Vulnogram 1.0.5"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2026-10-28T18:23:55.530504Z","id":"CVE-2026-93628","options":[{"Exploitation":"none"},{"Automatable":"yes"},{"Technical Impact":"partial"}],"role":"CISA Coordinator","version":"2.0.3"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-10-28T20:02:01.885Z"}}]}}}