CVE DatabaseCVE-2018-6882

Updated 2026-10-01한국어 권고문 →

CVE-2018-68826.1/MEDIUMCISA KEVCWE-79CWE-79

Zimbra Collaboration Suite (ZCS) Attachment Link Handling XSS Vulnerability (CVE-2018-6882) Analysis and Mitigation Guide

⚡ Jump to Patch

Affected Vendors

zimbra

Affected Components

zimbra_collaboration_suite

Published Date

2018-03-27

CVSS v3.1

6.1

MEDIUM

EPSS (30d)

29.8%

FIRST.org

CISA KEV

Exploited

NVD Source ↗

Executive & SecOps Summary

SECOPS ASSESSMENT

Affected Scope

Zimbra Collaboration Suite (ZCS) versions prior to 8.7 Patch 1 and 8.8.x versions prior to 8.8.7

Impact

Remote attackers can execute arbitrary web script or HTML in the victim's browser context via a manipulated Content-Location header in an email attachment, leading to session hijacking and account takeover

Mitigation

Immediately upgrade Zimbra Collaboration Suite to the latest patched version (8.7 Patch 1, 8.8.7, or later)

Affected Products & Version Scope

Zimbra Collaboration Suite (ZCS) versions before 8.7 Patch 1 and 8.8.x versions before 8.8.7

Remediation & Live Workaround Commands

PATCH & WORKAROUND

1. Official Patch & Version Upgrade Commands

Update the Zimbra official repository and upgrade the packages to the patched version. Use the following commands based on your operating system distribution.

bash

# For RedHat/CentOS-based systems
yum clean all
yum update zimbra-core zimbra-store -y

# For Ubuntu/Debian-based systems
apt-get update
apt-get --only-upgrade install zimbra-core zimbra-store -y

# Restart Zimbra services as the zimbra user
su - zimbra -c 'zmcontrol restart'

2. Temporary Workaround & Hardening Configuration

If an immediate upgrade is not feasible, configure a reverse proxy or Web Application Firewall (WAF) to filter out malicious scripts and enforce strict Content Security Policies (CSP).

nginx

# Nginx reverse proxy hardening configuration example
server {
    listen 443 ssl;
    server_name mail.yourdomain.com;

    # Enforce security headers to mitigate XSS
    add_header X-XSS-Protection '1; mode=block' always;
    add_header Content-Security-Policy "default-src 'self'; script-src 'self' 'unsafe-inline' 'unsafe-eval';" always;

    location / {
        proxy_pass http://zimbra_backend;
    }
}

3. Log Audit & IoC Verification Commands

Verify the currently running Zimbra version and scan the mail store and logs for potential exploitation attempts.

bash

# 1. Check the installed Zimbra version
su - zimbra -c 'zmcontrol -v'

# 2. Search for potential XSS payloads in Zimbra mailbox logs
grep -i 'javascript:' /opt/zimbra/log/mailbox.log

# 3. Scan stored email messages for suspicious Content-Location headers
find /opt/zimbra/store/ -type f -name '*.msg' | xargs grep -i 'Content-Location:.*javascript'

Interactive SecOps Remediation Checklist

0/4 (0%)

Recommended Security Control & Mitigation Partner

Cloudflare Enterprise & Pro WAF

Due to active exploitation in the wild (CISA KEV), immediately upgrade your Zimbra Collaboration Suite to a secure, patched version.

Block Exploits Instantly with Managed Virtual Patching Rules

Can't patch production immediately? Deploy managed WAF rules at the edge to intercept RCE, SQLi, and deserialization payloads before they hit your origin server.

3-min setup · Automated Zero-Day Managed Rules

Deploy Instant WAF Protection Free

Practice Exploiting & Patching This Web Vulnerability in an Interactive Lab

Launch Hands-On Security Lab

Technical Root Cause & Exploitation Mechanics

1. Vulnerability Overview & Root Cause

This vulnerability (CVE-2018-6882) is a Cross-Site Scripting (XSS) flaw residing within the ZmMailMsgView.getAttachmentLinkHtml function of Zimbra Collaboration Suite (ZCS). The root cause is the lack of proper input validation and output sanitization of the Content-Location header value of email attachments before rendering it as an HTML link in the user interface.

2. Exploitation Mechanics & Attack Scenario

An attacker crafts a malicious email containing an attachment with a specially designed Content-Location header (e.g., containing a javascript: URI or malicious HTML tags). When an authenticated user opens the email in the ZCS web client, the application processes the attachment and renders the link using the unsanitized header value, triggering the execution of the attacker's script within the victim's active session. This vulnerability is listed in CISA's KEV catalog, indicating active exploitation in the wild.

3. Infrastructure & Business Impact

Successful exploitation allows attackers to steal active session cookies, hijack user accounts, and gain unauthorized access to sensitive mailboxes. This can lead to data exfiltration, business email compromise (BEC) campaigns, and lateral movement within the corporate network.

Official Vendor Advisories & References

NVD Original English Description

Cross-site scripting (XSS) vulnerability in the ZmMailMsgView.getAttachmentLinkHtml function in Zimbra Collaboration Suite (ZCS) before 8.7 Patch 1 and 8.8.x before 8.8.7 might allow remote attackers to inject arbitrary web script or HTML via a Content-Location header in an email attachment.

http://seclists.org/fulldisclosure/2018/Mar/52

Source: cve@mitre.org · Mailing List, Third Party Advisory

http://www.securityfocus.com/archive/1/541891/100/0/threaded

Source: cve@mitre.org · Broken Link, Third Party Advisory, VDB Entry

https://bugzilla.zimbra.com/show_bug.cgi?id=108786

Source: cve@mitre.org · Broken Link, Issue Tracking, Permissions Required

https://wiki.zimbra.com/wiki/Zimbra_Releases/8.8.7

Source: cve@mitre.org · Permissions Required

https://wiki.zimbra.com/wiki/Zimbra_Security_Advisories

Source: cve@mitre.org · Vendor Advisory

https://www.securify.nl/advisory/SFY20180101/cross-site-scripting-vulnerability-in-zimbra-collaboration-suite-due-to-the-way-it-handles-attachment-links.html

Source: cve@mitre.org · Exploit, Third Party Advisory

Frequently Asked SecOps Questions (CVE-2018-6882)

FAQ

Q1. How critical is CVE-2018-6882 and is it actively exploited in the wild?

CVE-2018-6882 is rated CVSS 6.1 (MEDIUM) with a 30-day EPSS exploitation probability of 29.8%. It is listed in the CISA Known Exploited Vulnerabilities (KEV) catalog, requiring immediate emergency remediation.

Q2. Which vendors and products are affected by CVE-2018-6882?

Primary impacted vendors include zimbra across zimbra_collaboration_suite. Scope summary: Zimbra Collaboration Suite (ZCS) versions before 8.7 Patch 1 and 8.8.x versions before 8.8.7

Q3. What temporary mitigations or workarounds exist for CVE-2018-6882 before patching?

[Mitigation] Immediately upgrade Zimbra Collaboration Suite to the latest patched version (8.7 Patch 1, 8.8.7, or later) Follow the CLI remediation commands and interactive SecOps checklist on this page to restrict exposure prior to your maintenance window.

SECOPS WORKBENCH INTEGRATION

Generate an Internal Engineering Notice or CISO Report for CVE-2018-6882

Instantly format this advisory into an executive CISO summary or engineering patch ticket.

Generate Report →

🔗 Related Advisories in Similar Stack (zimbra)

View Category →

CVE-2026-735708.9/HIGHCISA KEV

EPSS 71.7%

Zimbra Collaboration Suite (ZCS) Remote Code Execution Vulnerability Advisory (CVE-2026-73570, CISA KEV Listed)

[Affected Scope] Zimbra Collaboration (ZCS) versions prior to 10.1.20, specifically when the optional zimbra-snmp package is installed and SNMP notifications are enabled.

CVE-2026-428976.1/MEDIUMCISA KEV

EPSS 70.7%