{"schema":"threatline.record/2","record":{"id":"CVE-2026-93628","aliases":[],"summary":"Zimbra Collaboration Suite Calendar Processing Authentication Bypass via Forged iCalendar REPLY Attendee Response","details":"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 An attacker who knows the meeting UID, organizer address and attendee address can send a non-outdated reply that changes the attendee's participation status in the organizer's calendar.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.","categories":["Applications & CMS"],"product":"Zimbra Collaboration Suite","vendor":"Zimbra","ecosystem":null,"affected_ranges":[{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2026-93628","source_modified_at":"2026-10-23T13:18:16.368Z","fetched_at":"2026-10-23T18:42:43.628194Z","product":"Zimbra Collaboration Suite","vendor":"Zimbra","versions":[{"lessThanOrEqual":"10.1.21","status":"affected","version":"0","versionType":"semver"}],"defaultStatus":"unaffected"}],"fixed_versions":[],"cvss":5.3,"severity":"Medium","kev":{"listed":false},"epss":{"probability":0.00376,"percentile":0.30431,"score_date":"2026-10-24"},"published_at":"2026-10-23T13:18:16.368Z","modified_at":"2026-10-23T13:18:16.368Z","provenance":[{"source":"CVE List","url":"https://www.cve.org/CVERecord?id=CVE-2026-93628","fetched_at":"2026-10-23T18:42:43.628194Z","source_modified_at":"2026-10-23T13:18:16.368Z"},{"source":"EPSS","url":"https://api.first.org/data/v1/epss?cve=CVE-2026-93628","fetched_at":"2026-10-24T18:03:20.872036Z","source_modified_at":"2026-10-24"}],"sources":["CVE List","EPSS"],"references":[{"source":"CVE List","url":"https://wiki.zimbra.com/wiki/Zimbra_Security_Advisories","tags":["vendor-advisory"]},{"source":"CVE List","url":"https://www.rapid7.com/blog/post/ve-breaking-zimbra-identity-boundaries-part-1/","tags":["related"]}],"locations":[],"motoko_assessment":{"status":"requires_architecture_review","automatic_remediation":false},"cve_state":"PUBLISHED","cvss_source":"CVE List","classification":{"method":"product-first software-layer rules","rules_version":"2.1","matched_on":"product","confidence":"heuristic","reviewed":false},"change_timestamp":"2026-10-23T13:18:16.368Z","content_hash":"0f58d743b5716092be926ae6cc92e424953414c4ec38093c368801f638ab8480"}}