CVE-2021-21396 Explained : Impact and Mitigation

A detailed article about the CVE-2021-21396 security vulnerability in wire-server, affecting versions from 2021-02-16 to 2021-03-02.

Understanding CVE-2021-21396

This CVE relates to the exposure of client metadata in the wire-server

GET /users/list-clients

endpoint between February 16, 2021, and March 2, 2021.

What is CVE-2021-21396?

In wire-server versions between 2021-02-16 and 2021-03-02, the client metadata of all users was exposed in the

/list-clients

endpoint, allowing unauthorized users to access sensitive information such as user IDs, device registration details, and cookies.

The Impact of CVE-2021-21396

The vulnerability had a CVSS base score of 6.5, with high confidentiality impact but low privileges required for exploitation. It exposed critical user information, posing a risk to user privacy and security.

Technical Details of CVE-2021-21396

This section discusses the technical aspects of the CVE.

Vulnerability Description

The flaw allowed any authenticated user to access client metadata without proper authentication, leading to potential data breaches and privacy violations.

Affected Systems and Versions

wire-server versions from 2021-02-16 to 2021-03-02 were impacted by this vulnerability, putting user data at risk.

Exploitation Mechanism

Attackers with access to the system could exploit the exposed endpoint to gather sensitive user information without proper authorization.

Mitigation and Prevention

Here's how to address the CVE-2021-21396 security issue.

Immediate Steps to Take

To mitigate the vulnerability, users are advised to remove

/list-clients

from the nginx configuration and update to wire-server version 2021-03-02 or later.

Long-Term Security Practices

Implement strict access controls, regularly monitor for unauthorized access, and maintain up-to-date software to prevent similar vulnerabilities.

Patching and Updates

Ensure timely installation of patches and updates provided by the wire-server project to address security flaws and enhance system security.