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CVE-2026-93638— Zimbra Collaboration Suite Pre-Authentication Reflected Cross-Site Scripting via Login Page zrememberme Parameter

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）登录页面存在反射型跨站脚本（XSS）漏洞，允许未认证的攻击者通过参数执行 JavaScript 代码。攻击者构造的重新登录 URL 会触发双因素认证错误提示，该提示将参数未经 HTML 编码地插入到隐藏输入框的属性中。当受害者访问该 URL 时，将在合法的 Zimbra 域名下加载由攻击者控制的脚本和页面内容，从而可通过伪造的登录表单窃取用户凭据。由于重新登录路径会在渲染攻击载荷前注销现有会话，因此演示的攻击无法继承原会话的邮箱访问权限。受影响的版本为 ZCS 10.1.16 和

CVSS 6.1 · Medium Updated Oct 23, 2026

Possible ATT&CK Techniques 3 AI

T1566 · Phishing T1055.001 · Dynamic-link Library Injection T1190 · Exploit Public-Facing Application

Affected Version Matrix 1

Vendor	Product	Version Range	Status
Zimbra	Zimbra Collaboration Suite	`≤ 10.1.17`	affected

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Vulnerability Information

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Vulnerability Title

Zimbra Collaboration Suite Pre-Authentication Reflected Cross-Site Scripting via Login Page zrememberme Parameter

Source: CVE Program / CVE List V5

Vulnerability Description

A reflected cross-site scripting vulnerability in the login page of Zimbra Collaboration Suite (ZCS) allows an unauthenticated attacker to execute JavaScript through the zrememberme parameter. A crafted relogin URL selects a two-factor error display that inserts the parameter into a hidden input attribute without HTML encoding. A victim who opens the URL receives attacker-controlled script and page content under the legitimate Zimbra origin, allowing credential capture through a replacement login form. The relogin path logs out an existing session before rendering the payload, so the demonstrated attack does not inherit that session's mailbox access. ZCS 10.1.16 and 10.1.17 are affected.

Source: CVE Program / CVE List V5

CVSS Information

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/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	0 ~ 10.1.17	-

II. Public POCs for CVE-2026-93638

#	POC Description	Source Link	Shenlong Link

AI-Generated POC Premium

No public POC found.

III. Intelligence Information for CVE-2026-93638

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Vendor Advisories for CVE-2026-93638 (1)

Zimbra Security Advisories - Zimbra :: Tech Center vendor-advisory

Other References for CVE-2026-93638 (1)

https://www.rapid7.com/blog/post/ve-breaking-zimbra-identity-boundaries-part-1/ related

https://www.cve.org/CVERecord?id=CVE-2026-93638

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-2026-93633	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-2026-93628	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-79

V. Comments for CVE-2026-93638

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Goal Reached Thanks to every supporter — we hit 100%!

CVE-2026-93638— Zimbra Collaboration Suite Pre-Authentication Reflected Cross-Site Scripting via Login Page zrememberme Parameter

Quick assessment

Possible ATT&CK Techniques 3 AI

Affected Version Matrix 1

I. Basic Information for CVE-2026-93638

Vulnerability Information

Vulnerability Title

Vulnerability Description

CVSS Information

Vulnerability Type

Affected Products

II. Public POCs for CVE-2026-93638

III. Intelligence Information for CVE-2026-93638

Vendor Advisories for CVE-2026-93638 (1)

Other References for CVE-2026-93638 (1)

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

IV. Related Vulnerabilities

V. Comments for CVE-2026-93638

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