Quiet Timing Attack Vulnerability in Token Verification Allowing Account Access

A timing attack vulnerability has been identified in Quiet, a decentralized messaging application, in versions prior to 6.0.1. The issue arises from the use of an insecure, non-constant-time comparison function for token verification in the application's API that facilitates backend and frontend communication. This flaw allowed attackers to exploit timing discrepancies in the response to guess tokens one character at a time. Successful exploitation could lead to unauthorized access to the user's Quiet account until the application is restarted, at which point the token is refreshed. The vulnerability could also be used to generate an invite link for accessing the user's community after the vulnerability is patched.

Impact

Exploitation of this vulnerability could result in unauthorized access to a user's Quiet account, allowing the attacker to access private messages and community invites. According to Quiet, this vulnerability could be exploited under certain conditions, such as through a malicious app or browser extension, or from another user account.

Reproduction

The vulnerability can be reproduced by using a token verification method that does not compare tokens in constant time. This can be done by sending different token values and measuring the response time, allowing for the inference of correct token characters based on the timing of the responses. This attack could be executed in a malicious application or browser extension on the same device, taking advantage of the lack of effective app sandboxing on mobile.

Remediation

Users are advised to upgrade to Quiet version 6.0.1 or later, leave their current community, and create a new one.