CVE-2022-21690 in OnionShare
Summary
by MITRE • 01/19/2022
OnionShare is an open source tool that lets you securely and anonymously share files, host websites, and chat with friends using the Tor network. In affected versions The path parameter of the requested URL is not sanitized before being passed to the QT frontend. This path is used in all components for displaying the server access history. This leads to a rendered HTML4 Subset (QT RichText editor) in the Onionshare frontend.
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Analysis
by VulDB Data Team • 01/20/2022
CVE-2022-21690 represents a cross-site scripting vulnerability in OnionShare, a tool designed for secure anonymous file sharing and web hosting over the Tor network. The vulnerability stems from insufficient input sanitization of the path parameter within HTTP requests, which directly impacts the application's Qt-based graphical user interface. When users access the application's web interface, the unsanitized path parameter gets processed and rendered within the Qt RichText editor component, creating a potential attack vector for malicious actors. This flaw exists specifically in how OnionShare handles URL path components before displaying them in the server access history logs, making it a classic case of improper input validation and output encoding.
The technical exploitation of this vulnerability occurs through manipulation of the URL path parameter during HTTP requests to the OnionShare service. When the application processes these requests, it fails to properly sanitize the path data before passing it to the Qt frontend's rich text rendering engine. This creates an environment where maliciously crafted path parameters can contain HTML or JavaScript code that gets executed within the context of the application's user interface. The vulnerability is particularly concerning because it affects the server access history display functionality, which means any user interaction with the application's web interface could potentially trigger the malicious code execution. The Qt RichText editor's handling of untrusted input creates a direct pathway for attackers to inject and execute arbitrary code within the application's graphical environment.
The operational impact of CVE-2022-21690 extends beyond simple code execution, as it undermines the security model that OnionShare is designed to provide. Since the application operates within the Tor network and is intended for anonymous communication, this vulnerability could allow attackers to compromise user sessions or gain unauthorized access to system resources. The attack surface is particularly broad because the vulnerability affects all components that display server access history, meaning that any interaction with the application's web interface could potentially be exploited. This creates a persistent risk for users who may unknowingly encounter maliciously crafted URLs, especially in environments where the application might be used for sensitive communications. The vulnerability also represents a failure in the application's defense-in-depth strategy, as it demonstrates inadequate input validation at multiple layers of the application architecture.
Mitigation strategies for CVE-2022-21690 should focus on implementing proper input sanitization and output encoding mechanisms within the Qt frontend components. The most effective approach involves sanitizing all user-supplied path parameters before they are processed by the Qt RichText editor, ensuring that any potentially malicious content is neutralized or removed. Organizations should also consider implementing content security policies that prevent the execution of embedded scripts within the application's interface. The fix should align with CWE-79, which specifically addresses cross-site scripting vulnerabilities, and should incorporate defensive programming practices that prevent improper handling of untrusted data. Additionally, the application should implement proper input validation at the earliest possible stage in the request processing pipeline, ensuring that path parameters are validated against expected formats before any rendering occurs. Security updates should be prioritized for all affected versions of OnionShare, and users should be advised to upgrade immediately to prevent exploitation of this vulnerability in environments where anonymity and security are paramount.