CVE-2017-5620 in Zammad
Summary
by MITRE
An XSS issue was discovered in Zammad before 1.0.4, 1.1.x before 1.1.3, and 1.2.x before 1.2.1. Attachments are opened in a new tab instead of getting downloaded. This creates an attack vector of executing code in the domain of the application.
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Analysis
by VulDB Data Team • 09/06/2020
The vulnerability identified as CVE-2017-5620 represents a cross-site scripting flaw in the Zammad helpdesk application that affects multiple version ranges including pre-1.0.4, pre-1.1.3, and pre-1.2.1 releases. This security weakness stems from the application's improper handling of file attachments that are opened in new browser tabs rather than being downloaded directly. The technical implementation of this vulnerability creates a dangerous attack surface where malicious actors can craft specially crafted attachment names or content that when opened in a new tab executes arbitrary JavaScript code within the context of the Zammad application's domain. This specific flaw aligns with CWE-79, which categorizes cross-site scripting vulnerabilities as weaknesses that allow attackers to inject malicious scripts into web applications viewed by other users.
The operational impact of this vulnerability extends beyond simple script execution as it provides attackers with the ability to perform session hijacking, data exfiltration, and privilege escalation within the application's security boundaries. When users click on malicious attachments that open in new tabs, the browser context allows the injected scripts to access the application's session cookies, potentially enabling attackers to impersonate legitimate users and gain unauthorized access to sensitive information. The vulnerability is particularly concerning because it leverages the trust relationship between the user and the application, making it difficult to detect through traditional security monitoring approaches. The attack vector is simplified by the fact that users must simply click on an attachment link, requiring no additional social engineering beyond the initial compromise of the attachment itself.
Security professionals should recognize this vulnerability as part of the broader ATT&CK framework's initial access and execution tactics, where adversaries leverage application weaknesses to establish footholds within target environments. The vulnerability's remediation requires proper input validation and output encoding of all user-supplied data, particularly in contexts where attachments are processed and displayed. Organizations should implement comprehensive content security policies that restrict script execution in contexts where user-generated content is rendered, while also ensuring that all file attachments are properly sanitized and validated before being processed. The fix involves implementing strict validation of attachment names and content types, combined with proper HTML escaping mechanisms that prevent malicious scripts from executing in the application's domain. Regular security updates and patch management processes become critical to prevent exploitation of this vulnerability, as the flaw represents a fundamental security weakness that could be exploited by threat actors with minimal technical expertise.
This vulnerability demonstrates the importance of secure file handling practices in web applications, particularly when dealing with user-uploaded content that gets processed and displayed. The improper handling of file attachments creates an attack surface that can be exploited through simple user interaction, making it a particularly dangerous weakness in applications that process sensitive information. Security teams should conduct regular vulnerability assessments focusing on input validation and output encoding mechanisms, ensuring that all user-supplied data is properly sanitized before being rendered in web contexts. The remediation process must include comprehensive testing of attachment handling functionality to verify that no similar vulnerabilities exist in related components, as this type of flaw often indicates broader security implementation gaps within the application architecture.