---
id: CVE-2026-93629
title: >-
  Zimbra Collaboration Suite Calendar Processing Authentication Bypass via
  Forged iCalendar REQUEST Organizer Identity
summary: >-
  An organizer authentication vulnerability in Zimbra Collaboration Suite (ZCS)
  allows an unauthenticated email sender to insert calendar invitations
  attributed to another user. The email delivery path permits external
  invitations but does…
severity: medium
cvss: 5.3
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N'
cvssSource: cna
cwe:
  - CWE-290
vendor: Zimbra
product: Zimbra Collaboration Suite
affected:
  - collaboration_suite <= 10.1.21
published: '2026-10-23'
updated: '2026-10-23'
sourceUpdated: '2026-10-23T13:19:26.405Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-93629'
references:
  - url: 'https://wiki.zimbra.com/wiki/Zimbra_Security_Advisories'
  - url: >-
      https://www.rapid7.com/blog/post/ve-breaking-zimbra-identity-boundaries-part-1/
tags:
  - cve.org
ingestedAt: '2026-10-23T14:28:08.715Z'
---

## Overview

An organizer authentication vulnerability in Zimbra Collaboration Suite (ZCS) allows an unauthenticated email sender to insert calendar invitations attributed to another user. The email delivery path permits external invitations but does not verify that the message sender is authorized to use the iCalendar ORGANIZER identity. When automatic invitation insertion is enabled, a crafted REQUEST component creates an event containing attacker-selected meeting details and reminders under a forged organizer without recipient interaction. No corresponding event is created in the claimed organizer's calendar. ZCS 10.1.16 and 10.1.21 are affected.

## Affected

- `collaboration_suite <= 10.1.21`

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.