CVE-2016-3408 in Zimbra Collaboration
Summary
by MITRE
Cross-site scripting (XSS) vulnerability in Zimbra Collaboration before 8.7.0 allows remote attackers to inject arbitrary web script or HTML via unspecified vectors, aka bug 101813.
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Analysis
by VulDB Data Team • 05/13/2026
The CVE-2016-3408 vulnerability represents a critical cross-site scripting flaw discovered in Zimbra Collaboration software prior to version 8.7.0, classified under the Common Weakness Enumeration category CWE-79 which specifically addresses improper neutralization of input during web page generation. This vulnerability falls within the broader ATT&CK framework under the T1059.008 technique for Command and Scripting Interpreter, specifically targeting web-based attack surfaces through client-side script injection mechanisms. The vulnerability allows remote attackers to execute arbitrary web scripts or HTML content within the context of authenticated users, potentially compromising the entire user session and sensitive data exposure.
The technical flaw manifests through unspecified vectors within the Zimbra Collaboration platform's input validation and output encoding mechanisms, which fail to properly sanitize user-supplied data before rendering it in web pages. This weakness creates an environment where malicious actors can craft specially formatted input that bypasses security controls designed to prevent script execution in web contexts. The vulnerability affects the web client interface components of Zimbra's email and collaboration platform, making it particularly dangerous as it can be exploited through various user interaction points including email content, calendar entries, and contact management features. Attackers typically leverage this vulnerability by embedding malicious scripts within legitimate-looking user data, which then executes in the browser of unsuspecting victims who interact with the compromised content.
The operational impact of CVE-2016-3408 extends beyond simple script execution to encompass complete session hijacking capabilities, data theft, and potential privilege escalation within the Zimbra environment. Successful exploitation can lead to unauthorized access to email accounts, calendar data, contact information, and potentially allow attackers to impersonate legitimate users for extended periods. The vulnerability's remote nature means attackers can exploit it without requiring physical access to systems or local network presence, making it particularly dangerous for enterprise environments where Zimbra serves as a primary communication platform. Organizations using vulnerable versions face significant risks including data breaches, insider threat exploitation, and compliance violations due to inadequate protection of sensitive email communications and collaboration data.
Organizations should implement immediate mitigations including upgrading to Zimbra Collaboration version 8.7.0 or later, which contains the necessary patches to address the XSS vulnerability. Additional protective measures include implementing comprehensive input validation policies, enabling strict content security policies, and deploying web application firewalls to monitor and filter suspicious traffic patterns. Security teams should conduct thorough vulnerability assessments to identify any potentially compromised user sessions and implement enhanced monitoring for unusual user behavior patterns that might indicate exploitation attempts. The remediation process should also include user education regarding phishing awareness and safe email handling practices, as the vulnerability can be exploited through social engineering vectors where users inadvertently interact with malicious content. Regular security testing and penetration testing should be conducted to verify that all input validation mechanisms are properly functioning and that no similar vulnerabilities exist within the Zimbra platform or related applications.