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CVE-2026-93647— Zimbra Collaboration Suite Classic Web Client Stored Cross-Site Scripting via Crafted Calendar COUNTER Message From Address

Quick assessment

Affected
Zimbra Zimbra Collaboration Suite (ZCS)
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.

未经身份验证的日历发送者可以在 COUNTER 消息的 RFC From 地址中注入可执行的标记内容。在 Zimbra Classic 中选中该消息时，会触发存储型跨站脚本漏洞（Stored XSS），使攻击者能够访问用户的邮箱数据，并以受害者身份进行操作。

CVSS 9.3 · Critical EPSS 0.23% · P12

Affected Version Matrix 1

VendorProduct Version RangeStatus
Zimbra Zimbra Collaboration Suite (ZCS) < 10.1.21 affected
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I. Basic Information for CVE-2026-93647

Vulnerability Information
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Vulnerability Title
Zimbra Collaboration Suite Classic Web Client Stored Cross-Site Scripting via Crafted Calendar COUNTER Message From Address
Source: CVE Program / CVE List V5
Vulnerability Description
An unauthenticated calendar sender can place active markup in a COUNTER message's RFC From address. Selecting the message in Zimbra Classic triggers stored XSS, allowing the attacker to access mailbox data and act as the victim.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
在Web页面生成时对输入的转义处理不恰当(跨站脚本)
Source: CVE Program / CVE List V5

Affected Products

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

II. Public POCs for CVE-2026-93647

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III. Intelligence Information for CVE-2026-93647

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Vendor Advisories for CVE-2026-93647 (1)

Same Patch Batch · Zimbra · 2026-09-25 · 4 CVEs total

CVE-2026-93643 9.8 CRITICAL Zimbra Collaboration Suite OnlyOffice Integration Path Traversal Leading to Remote Code Ex
CVE-2026-93642 9.3 CRITICAL Zimbra Collaboration Suite Modern Web Client Stored Cross-Site Scripting via Forged Share
CVE-2026-93641 9.3 CRITICAL Zimbra Collaboration Suite Classic Web Client Stored Cross-Site Scripting via Forged Share

IV. Related Vulnerabilities

Same product: Zimbra Collaboration Suite (ZCS)
Same vendor: Zimbra
Same weakness: CWE-79

V. Comments for CVE-2026-93647

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