CVE-2017-16782 in Home Assistant
Summary
by MITRE
In Home Assistant before 0.57, it is possible to inject JavaScript code into a persistent notification via crafted Markdown text, aka XSS.
If you want to get best quality of vulnerability data, you may have to visit VulDB.
Analysis
by VulDB Data Team • 01/10/2023
The vulnerability identified as CVE-2017-16782 affects Home Assistant versions prior to 0.57, representing a critical cross-site scripting vulnerability that allows remote attackers to execute malicious JavaScript code within the application's persistent notification system. This flaw specifically resides in how the system processes Markdown text input, creating an avenue for attackers to inject malicious code that gets executed when notifications are displayed to users. The vulnerability stems from insufficient input validation and sanitization of user-provided content, particularly when handling Markdown formatted text that is intended to be rendered as notifications within the Home Assistant interface.
The technical implementation of this vulnerability involves the improper handling of Markdown content within the persistent notification framework of Home Assistant. When users or attackers provide crafted Markdown text containing JavaScript code, the application fails to adequately sanitize this input before rendering it as HTML. This processing chain typically involves converting Markdown to HTML, which then gets displayed in the notification interface without proper security controls. The flaw allows attackers to inject script tags, event handlers, or other malicious JavaScript payloads that execute in the context of the victim's browser session. This represents a classic cross-site scripting vulnerability that can be exploited through user input fields or API endpoints that accept Markdown formatted content for notification purposes.
The operational impact of this vulnerability extends beyond simple code execution, as it can enable attackers to perform a wide range of malicious activities within the compromised environment. An attacker could potentially steal user session cookies, redirect users to malicious websites, modify the application interface, or even escalate privileges if the application runs with elevated permissions. The persistent notification system makes this particularly dangerous since notifications are designed to be displayed to users regularly, ensuring that the injected JavaScript code executes each time a notification is shown. This vulnerability affects all users of affected Home Assistant installations, making it a significant security risk for home automation systems that may contain sensitive personal data or control critical infrastructure.
Mitigation strategies for CVE-2017-16782 should focus on implementing robust input validation and sanitization mechanisms within the Home Assistant application. The primary fix involves upgrading to version 0.57 or later where proper Markdown sanitization has been implemented to prevent script injection. Organizations should also consider implementing Content Security Policy headers to limit script execution, employing proper HTML escaping for all user-generated content, and implementing input length restrictions for notification fields. Security teams should conduct regular vulnerability assessments of their home automation systems and ensure that all components are kept up to date with the latest security patches. This vulnerability aligns with CWE-79 which describes cross-site scripting flaws, and can be mapped to ATT&CK technique T1059.007 for scripting languages, demonstrating how attackers can leverage input validation bypasses to execute malicious code within web applications.
The broader implications of this vulnerability highlight the importance of secure input handling in web applications, particularly those designed for user interaction. Home Assistant systems often integrate with various IoT devices and personal data sources, making them attractive targets for attackers seeking to exploit security weaknesses. The vulnerability demonstrates how seemingly benign features like notification systems can become attack vectors when proper security controls are not implemented. Organizations should implement comprehensive security testing practices including dynamic application security testing and static code analysis to identify similar input validation flaws in their applications. This vulnerability also underscores the necessity of keeping home automation systems updated, as these devices often run for extended periods without regular maintenance or security updates, creating persistent security risks for users who may not be aware of available patches.