CVE-2019-8946 in Zimbra Collaboration
Summary
by MITRE
Zimbra Collaboration 8.7.x - 8.8.11P2 contains persistent XSS.
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Analysis
by VulDB Data Team • 03/27/2024
The vulnerability identified as CVE-2019-8946 represents a critical persistent cross-site scripting flaw within Zimbra Collaboration software versions ranging from 8.7.x through 8.8.11P2. This security weakness allows attackers to inject malicious scripts into the web application's user interface, creating a persistent threat that can affect multiple users over time. The vulnerability stems from insufficient input validation and output encoding mechanisms within the email client's web interface, where user-supplied data is not adequately sanitized before being rendered back to other users. This flaw specifically impacts the web-based administration console and user interface components that process email content, attachments, and user-generated parameters.
The technical implementation of this vulnerability occurs when the application fails to properly escape or encode special characters in user input fields, particularly within email headers, message bodies, and administrative configuration parameters. Attackers can exploit this weakness by crafting malicious payloads that contain script tags or other XSS vectors within email content or administrative settings. When other users view the compromised content through the web interface, the embedded scripts execute in their browsers, potentially leading to session hijacking, credential theft, or redirection to malicious sites. The persistence aspect means that once the malicious content is injected, it remains active and affects all users who encounter it without proper sanitization mechanisms in place.
The operational impact of CVE-2019-8946 extends beyond simple script execution, as it provides attackers with a foothold for more sophisticated attacks within the email ecosystem. This vulnerability aligns with CWE-79 which specifically addresses cross-site scripting flaws, and can be mapped to ATT&CK technique T1566.001 for initial access through spearphishing with attachments or links. The attack surface includes email administrators, end users, and potentially system administrators who may inadvertently click on malicious links or view compromised emails. Successful exploitation could lead to unauthorized access to sensitive email communications, compromise of user sessions, and potential lateral movement within the organization's network infrastructure where Zimbra serves as a central communication platform.
Mitigation strategies for this vulnerability require immediate implementation of proper input validation and output encoding mechanisms throughout the Zimbra web application. Organizations should apply the vendor-provided patches and updates released for versions 8.8.12 and later, which address the XSS vulnerability through enhanced sanitization of user inputs and improved HTML escaping. Network segmentation and monitoring solutions should be deployed to detect anomalous script execution patterns within email traffic. Additionally, implementing content security policies, disabling unnecessary administrative features, and conducting regular security assessments of the email infrastructure can help reduce the attack surface. Security teams should also establish user awareness programs to prevent social engineering attacks that might leverage this vulnerability, while maintaining detailed logging of administrative activities and user access patterns to detect potential exploitation attempts.