CVE-2017-6503 in qBittorrent
Summary
by MITRE
WebUI in qBittorrent before 3.3.11 did not escape many values, which could potentially lead to XSS.
Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.
Analysis
by VulDB Data Team • 09/04/2020
The vulnerability identified as CVE-2017-6503 affects the WebUI component of qBittorrent software versions prior to 3.3.11. This issue represents a classic cross-site scripting vulnerability that arises from inadequate output sanitization within the web interface. The qBittorrent application is a popular open-source BitTorrent client that provides a web-based user interface for remote management and control of torrent downloads. The WebUI functionality allows users to monitor and manage their torrent activities through a browser-based interface, making it a critical component for remote administration capabilities.
The technical flaw stems from the WebUI's failure to properly escape or sanitize user-supplied input values before rendering them in the browser context. When qBittorrent processes data from various sources including torrent names, file names, tracker URLs, and other user-provided content, it does not adequately sanitize this information before displaying it within the web interface. This omission creates an environment where maliciously crafted input can be executed as script code within the browser of any user who views the affected content. The vulnerability specifically impacts how the application handles numerous data fields that are directly rendered in HTML output without proper context-aware escaping mechanisms.
The operational impact of this vulnerability extends beyond simple script execution, as it provides attackers with potential access to user sessions and sensitive data within the qBittorrent environment. An attacker could craft malicious torrent files or manipulate tracker URLs containing embedded script code that would execute when other users view these elements through the WebUI. This could lead to session hijacking, data theft, or even complete compromise of the affected system if users have administrative privileges. The vulnerability is particularly concerning in environments where multiple users access the same qBittorrent instance, as it could enable attackers to execute arbitrary code on behalf of other users or gain unauthorized access to the torrent management system.
Security professionals should note that this vulnerability aligns with CWE-79, which specifically addresses Cross-Site Scripting flaws in software applications. The issue demonstrates poor input validation and output encoding practices that are fundamental to preventing XSS attacks. From an adversary perspective, this vulnerability maps to ATT&CK technique T1059.007 for Command and Scripting Interpreter: JavaScript, as it enables attackers to execute JavaScript code within the victim's browser context. The attack surface is significant since the WebUI is designed for remote access and often runs on systems with network exposure, making it an attractive target for exploitation. Organizations using qBittorrent should prioritize immediate patching to version 3.3.11 or later, which implements proper output escaping mechanisms to prevent this vulnerability from being exploited.
The remediation strategy involves ensuring that all user-supplied input values are properly escaped or encoded before being rendered in HTML contexts. This includes implementing context-aware escaping for different output types including HTML content, JavaScript contexts, and attribute values. Security teams should also consider implementing Content Security Policy headers as an additional defense-in-depth measure to further mitigate the impact of any potential XSS vulnerabilities. Regular security assessments of web applications and input validation mechanisms remain essential practices for preventing similar vulnerabilities from emerging in other software components.