CVE-2026-93627

Zimbra Collaboration Suite Calendar Processing Authentication Bypass via Forged iCalendar CANCEL/REQUEST Organizer

Published Oct 23, 2026 CVSS 3.1 · 5.3 Medium EPSS < 1% KEV · Not listed
Description
An organizer authentication vulnerability in the email calendar processing of Zimbra Collaboration Suite (ZCS) allows an unauthenticated sender to cancel or modify an existing meeting in a recipient's calendar. Zimbra accepts iCalendar CANCEL and REQUEST components without verifying that the email sender is authorized to act as the supplied organizer. An attacker who knows the meeting UID and organizer address can supply a non-outdated sequence number to move the recipient's meeting to Trash or replace its details. Processing occurs automatically during email delivery without recipient interaction. ZCS 10.1.16 and 10.1.21 are affected.

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

No advisories available
History
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Type Values Removed Values Added
First Time appeared Zimbra
Zimbra zimbra Collaboration Suite
Vendors & Products Zimbra
Zimbra zimbra Collaboration Suite
Type Values Removed Values Added
Description An organizer authentication vulnerability in the email calendar processing of Zimbra Collaboration Suite (ZCS) allows an unauthenticated sender to cancel or modify an existing meeting in a recipient's calendar. Zimbra accepts iCalendar CANCEL and REQUEST components without verifying that the email sender is authorized to act as the supplied organizer. An attacker who knows the meeting UID and organizer address can supply a non-outdated sequence number to move the recipient's meeting to Trash or replace its details. Processing occurs automatically during email delivery without recipient interaction. ZCS 10.1.16 and 10.1.21 are affected.
Title Zimbra Collaboration Suite Calendar Processing Authentication Bypass via Forged iCalendar CANCEL/REQUEST Organizer
Weaknesses CWE-290
References
Metrics cvssV3_1

{'score': 5.3, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
rapid7
Published
Updated
Oct 28, 2026, 8:02 PM
Reserved
Sep 18, 2026, 12:22 PM
Status
Undergoing Analysis
Published
Oct 23, 2026, 2:17 PM
Modified
Oct 28, 2026, 8:18 PM