CVE-2017-8783 in Zimbra Collaboration
Summary
by MITRE
Synacor Zimbra Collaboration Suite (ZCS) before 8.7.10 has Persistent XSS.
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Analysis
by VulDB Data Team • 02/03/2020
The Synacor Zimbra Collaboration Suite represents a widely deployed enterprise email and collaboration platform that serves millions of users across organizations globally. This particular vulnerability affects versions prior to 8.7.10 and specifically targets the web interface component where users interact with the system through their browsers. The vulnerability manifests as a persistent cross-site scripting flaw that allows attackers to inject malicious scripts into the application's user interface, creating a significant security risk for organizations relying on this platform for their email communications and collaboration needs.
The technical implementation of this persistent XSS vulnerability occurs within the web application's input validation and output encoding mechanisms. Attackers can exploit this flaw by crafting malicious payloads that are stored within the application's database and subsequently executed whenever authenticated users view the affected content. The persistence aspect means that the malicious scripts remain active even after the initial injection, continuously affecting any user who accesses the compromised data. This type of vulnerability typically arises from insufficient sanitization of user-supplied input before rendering it in web pages, allowing attackers to inject HTML or JavaScript code that executes in the context of other users' browsers.
The operational impact of this vulnerability extends beyond simple script execution, as it can enable attackers to perform a wide range of malicious activities including session hijacking, credential theft, data exfiltration, and privilege escalation within the email system. An attacker who successfully exploits this vulnerability could gain access to sensitive email communications, calendar entries, contact information, and potentially escalate privileges to administrative functions within the Zimbra environment. The persistent nature of the vulnerability means that the attack can continue to affect users over extended periods, making it particularly dangerous for enterprise environments where email systems serve as critical communication infrastructure.
Organizations should prioritize immediate remediation by upgrading to Zimbra Collaboration Suite version 8.7.10 or later, which includes proper input validation and output encoding fixes. Additional mitigations include implementing web application firewalls to detect and block malicious payloads, restricting user input through enhanced validation rules, and conducting regular security assessments of the web application. The vulnerability aligns with CWE-79 Cross-site Scripting, which categorizes it as a weakness in input validation and output encoding. From an attacker perspective, this vulnerability maps to ATT&CK technique T1059.007 Command and Scripting Interpreter: JavaScript, as it enables attackers to execute malicious JavaScript code within user sessions. Security teams should also consider implementing Content Security Policy headers to limit script execution and establish comprehensive monitoring for unusual user activities that might indicate exploitation attempts.