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CVE-2026-93628— Zimbra Collaboration Suite Calendar Processing Authentication Bypass via Forged iCalendar REPLY Attendee Response

Quick assessment

Affected
Zimbra Zimbra Collaboration Suite
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Zimbra 协作套件（ZCS）在处理电子邮件日历时存在参会者身份认证漏洞，允许未经认证的发送者伪造其他参会者对现有会议的回复。Zimbra 在处理 iCalendar 的 REPLY 组件时传递了空发送者身份，导致参会者授权过滤器被跳过。如果攻击者知晓会议的 UID、组织者邮箱地址以及参会者邮箱地址，即可发送一份未过期的回复，从而在组织者的日历中更改该参会者的参与状态。该变更在邮件投递过程中自动发生，无需组织者或参会者进行任何交互。受影响的版本为 ZCS 10.1.16 和 10.1.21。

CVSS 5.3 · Medium
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I. Basic Information for CVE-2026-93628

Vulnerability Information
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Vulnerability Title
Zimbra Collaboration Suite Calendar Processing Authentication Bypass via Forged iCalendar REPLY Attendee Response
Source: CVE Program / CVE List V5
Vulnerability 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 An attacker who knows the meeting UID, organizer address and attendee address can send a non-outdated reply that changes the attendee's participation status in the organizer's calendar.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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
使用欺骗进行的认证绕过
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
Zimbra Zimbra Collaboration Suite 0 ~ 10.1.21 -

II. Public POCs for CVE-2026-93628

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III. Intelligence Information for CVE-2026-93628

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Vendor Advisories for CVE-2026-93628 (1)

Other References for CVE-2026-93628 (1)

Same Patch Batch · Zimbra · 2026-10-23 · 17 CVEs total

CVE-2026-10632 8.7 HIGH Zimbra Collaboration Suite Classic Web Client Reflected Cross-Site Scripting via Document
CVE-2026-50053 8.7 HIGH Zimbra Collaboration Suite RestFilter Request Attribute Override via Unauthenticated URL P
CVE-2026-93639 8.7 HIGH Zimbra Collaboration Suite Missing Authorization in ConfigureZimlet Enables Delegated Admi
CVE-2026-93640 7.8 HIGH Zimbra Collaboration Suite Local Privilege Escalation via Unrestricted zmunbound Sudo Conf
CVE-2026-50056 7.8 HIGH Zimbra Collaboration Suite Local Privilege Escalation via zmmailboxdmgr JVM Argument Injec
CVE-2026-50057 7.8 HIGH Zimbra Collaboration Suite Local Privilege Escalation via Unrestricted Postfix Sudo Permis
CVE-2026-93631 7.1 HIGH Zimbra Collaboration Suite OAuth Extension Cross-Site Request Forgery Enables Account Link
CVE-2026-115786 6.5 MEDIUM Zimbra Collaboration Suite Shared-File Mailbox Quota Accounting Error Enables Quota Exhaus
CVE-2026-93638 6.1 MEDIUM Zimbra Collaboration Suite Pre-Authentication Reflected Cross-Site Scripting via Login Pag
CVE-2026-93633 5.4 MEDIUM Zimbra Collaboration Suite Briefcase CSS Sanitization Bypass via Non-ASCII Stylesheet Char
CVE-2026-93629 5.3 MEDIUM Zimbra Collaboration Suite Calendar Processing Authentication Bypass via Forged iCalendar
CVE-2026-93627 5.3 MEDIUM Zimbra Collaboration Suite Calendar Processing Authentication Bypass via Forged iCalendar
CVE-2026-93630 4.3 MEDIUM Zimbra Collaboration Suite Email HTML Sanitizer Bypass via Hostname Canonicalization
CVE-2026-93634 4.3 MEDIUM Zimbra Collaboration Suite Cross-Account Authorization Bypass via Forged Shared-File Recor
CVE-2026-93636 4.3 MEDIUM Zimbra Collaboration Suite LDAP Filter Injection via Calendar Resource Attribute Name
CVE-2026-115785 4.3 MEDIUM Zimbra Collaboration Suite Data Source Test SMTP Command Injection via Unsanitized Email A

IV. Related Vulnerabilities

Same product: Zimbra Collaboration Suite
Same vendor: Zimbra
Same weakness: CWE-290

V. Comments for CVE-2026-93628

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