CVE-2022-21695 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 authenticated users (or unauthenticated in public mode) can send messages without being visible in the list of chat participants. This issue has been resolved in version 2.5.
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Analysis
by VulDB Data Team • 01/20/2022
The vulnerability identified as CVE-2022-21695 affects OnionShare, a widely-used open source tool designed for secure and anonymous file sharing, website hosting, and instant messaging through the Tor network. This tool operates by creating hidden services that enable users to communicate and share data without revealing their real IP addresses or locations, making it particularly valuable for privacy-conscious individuals and organizations. The security implications of this flaw are significant given OnionShare's primary purpose of providing anonymous communication channels.
The technical flaw in question resides in the chat functionality of OnionShare where authenticated users or those operating in public mode can send messages without being visible in the list of chat participants. This represents a violation of the expected privacy model that users rely upon when utilizing the application for anonymous communication. The vulnerability essentially allows for covert messaging where senders can bypass the normal visibility mechanisms that should track all active participants in a chat session, creating a scenario where some users can communicate while remaining invisible to others in the same chat room.
This issue directly impacts the operational integrity of OnionShare's anonymity features and can be classified under CWE-284, which deals with improper access control, and potentially CWE-310, related to cryptographic weakness. The vulnerability enables a form of stealth communication that undermines the transparency and visibility expected in collaborative chat environments. From an operational standpoint, this flaw could be exploited by malicious actors to conduct surveillance or send covert messages without detection by other participants, thereby compromising the trust model that OnionShare aims to maintain.
The attack surface for this vulnerability is particularly concerning as it affects both authenticated users and those operating in public mode, expanding the potential threat vectors. Users who rely on OnionShare for sensitive communications may unknowingly be subject to this vulnerability, where their presence in chat sessions could be obscured from other participants. This creates a potential for abuse where individuals can send messages without others being aware of their participation, which could be leveraged for social engineering attacks or to avoid detection in sensitive discussions.
The resolution of this issue in version 2.5 demonstrates that the developers recognized the severity of the privacy violation and implemented appropriate fixes to restore proper visibility controls in chat sessions. Organizations and individuals using OnionShare should immediately upgrade to version 2.5 or later to ensure that their communication channels maintain proper participant visibility and that the tool continues to function as intended for anonymous and secure communication. This vulnerability serves as a reminder of the critical importance of maintaining proper access controls and visibility mechanisms in anonymous communication systems, as these features are fundamental to the trust users place in such tools.
The broader implications of this vulnerability extend to the field of secure communication tools and highlight the challenges of maintaining anonymity while ensuring proper access control in distributed systems. This issue aligns with ATT&CK technique T1566, which involves social engineering through the manipulation of communication visibility, and demonstrates the importance of proper access control implementation in privacy-focused applications. The fix implemented by the OnionShare development team addresses the core issue of unauthorized covert communication within the application's chat functionality, restoring the expected behavior where all participants remain visible to each other during chat sessions.