CVE-2017-5621 in Zammad
Summary
by MITRE
An issue was discovered in Zammad before 1.0.4, 1.1.x before 1.1.3, and 1.2.x before 1.2.1. XSS can be triggered via malicious HTML in a chat message or the content of a ticket article, when using either the REST API or the WebSocket API.
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Analysis
by VulDB Data Team • 09/06/2020
The vulnerability identified as CVE-2017-5621 represents a cross-site scripting flaw in the Zammad helpdesk system that affects multiple version ranges including pre-1.0.4, pre-1.1.3, and pre-1.2.1 releases. This vulnerability stems from inadequate input sanitization mechanisms within the application's handling of user-provided content, specifically when processing chat messages and ticket article content through both REST and WebSocket APIs. The flaw allows attackers to inject malicious HTML code that executes in the context of other users' browsers, creating a persistent security risk for organizations relying on the platform for customer support and internal communication.
The technical exploitation of this vulnerability occurs through the manipulation of input fields within the Zammad application's communication channels. When users submit chat messages or create ticket articles containing malicious HTML content, the application fails to properly sanitize or escape these inputs before rendering them in the user interface. This improper handling of user-supplied data creates an environment where attacker-controlled scripts can execute with the privileges of authenticated users, potentially leading to session hijacking, data exfiltration, or further compromise of the affected system. The vulnerability is particularly concerning as it affects both REST and WebSocket API endpoints, expanding the attack surface and providing multiple vectors for exploitation.
The operational impact of CVE-2017-5621 extends beyond simple script execution, as it can enable attackers to perform sophisticated attacks such as credential theft, privilege escalation, and persistent backdoor establishment within the Zammad environment. Organizations utilizing this helpdesk system face significant risks including unauthorized access to sensitive customer data, disruption of support operations, and potential lateral movement within their network infrastructure. The vulnerability's presence in both chat and ticket article functionality means that attackers can compromise the system through various communication channels, making it particularly dangerous for organizations that rely heavily on user-generated content for their support workflows. This flaw directly relates to CWE-79 which categorizes cross-site scripting vulnerabilities as a critical security weakness in web applications.
Mitigation strategies for CVE-2017-5621 should prioritize immediate patching of affected Zammad installations to versions 1.0.4, 1.1.3, or 1.2.1 respectively, depending on the current deployment. Organizations should also implement additional defensive measures including input validation at multiple layers, content security policy enforcement, and regular security auditing of user-generated content. The implementation of proper HTML sanitization libraries and the enforcement of strict output encoding practices can significantly reduce the risk of exploitation. Security teams should monitor for suspicious activities in chat and ticket systems, particularly around user accounts that may have been compromised through this vulnerability. Organizations should also consider implementing web application firewalls and network monitoring solutions to detect and prevent exploitation attempts. This vulnerability aligns with ATT&CK technique T1059.007 which covers scripting through web shells, and T1566 which addresses social engineering through malicious web content, highlighting the multi-faceted nature of the threat posed by this XSS vulnerability.