CVE-2026-93628Medium· 5.3▾ SunlitAn 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 ident…
▾ Sunlit zone — Low / medium · no exploitation signal
impact 29.2 · likelihood 0 · exploitation 0
Need a working PoC? Pro members can cast a request and our team develops one — it lands right here.
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 An attacker who knows the meeting UID, organizer address and attendee address can send a non-outdated reply that changes the attendee's participation status in the organizer's calendar.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.
collaboration_suite <= 10.1.21Refer to the linked advisories for vendor-supplied fixes and affected version ranges.
Connected by shared product, vendor, weakness, or advisory.
CVE-2026-93629Medium· 5.3Zimbra Collaboration Suite Calendar Processing Authentication Bypass via Forged iCalendar REQUEST Organizer Identity
CVE-2026-93627Medium· 5.3Zimbra Collaboration Suite Calendar Processing Authentication Bypass via Forged iCalendar CANCEL/REQUEST Organizer
CVE-2026-93631High· 7.1Zimbra Collaboration Suite OAuth Extension Cross-Site Request Forgery Enables Account Linking
CVE-2026-93630Medium· 4.3Zimbra Collaboration Suite Email HTML Sanitizer Bypass via Hostname Canonicalization
CVE-2026-93636Medium· 4.3Zimbra Collaboration Suite LDAP Filter Injection via Calendar Resource Attribute Name
CVE-2026-93633Medium· 5.4Zimbra Collaboration Suite Briefcase CSS Sanitization Bypass via Non-ASCII Stylesheet Characters