CVE-2017-17703 in Zimbra Collaboration
Summary
by MITRE
Synacor Zimbra Collaboration Suite (ZCS) before 8.8.3 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 organizations globally for managing email services, calendaring, contacts, and document sharing. This particular vulnerability affects versions prior to 8.8.3 and introduces a critical persistent cross-site scripting flaw that allows attackers to inject malicious scripts into the application's user interface. The vulnerability exists within the platform's handling of user input and rendering processes, creating a persistent threat that can affect multiple users over time.
The technical flaw manifests when the application fails to properly sanitize or escape user-supplied input before rendering it within web pages. Attackers can exploit this weakness by crafting malicious payloads that get stored within the application's database or user interface elements, ensuring that the malicious script executes every time affected users view the compromised content. This persistent nature means that the vulnerability remains active until the malicious content is removed from the system, potentially affecting all users who encounter the compromised data. The flaw primarily impacts the web client interface where users interact with email messages, calendar entries, and other collaborative features.
The operational impact of this vulnerability extends beyond simple script execution, as it can enable attackers to steal session cookies, perform actions on behalf of users, access sensitive email communications, and potentially escalate privileges within the system. An attacker who successfully exploits this vulnerability can gain unauthorized access to user accounts, read confidential email messages, modify calendar entries, and access shared documents. The persistent nature of the attack means that even after initial exploitation, the malicious code continues to execute whenever users access the compromised data, creating an ongoing threat vector. This vulnerability directly relates to CWE-79 which describes Cross-Site Scripting flaws, and can be categorized under ATT&CK technique T1059.007 for script execution through web applications.
Organizations using affected versions of Zimbra Collaboration Suite should immediately upgrade to version 8.8.3 or later to remediate this vulnerability. Additionally, administrators should implement input validation controls, sanitize all user-supplied data, and monitor web application logs for suspicious activity. Network segmentation and web application firewalls can provide additional layers of protection, while user education about recognizing potentially malicious email content remains crucial. The vulnerability demonstrates the importance of proper input sanitization and output encoding in web applications, as outlined in OWASP Top Ten security principles and the secure coding guidelines established by NIST. Regular security assessments and penetration testing should be conducted to identify similar vulnerabilities in the application's codebase and prevent similar issues from arising in the future.