CVE-2021-23401 Explained : Impact and Mitigation

Flask-User package is affected by an Open Redirect vulnerability, allowing attackers to bypass URL validation and redirect users to arbitrary URLs. This CVE was reported by Noam Moshe of Claroty on July 5, 2021.

Understanding CVE-2021-23401

This section dives into the details of the Flask-User Open Redirect vulnerability.

What is CVE-2021-23401?

CVE-2021-23401 refers to an Open Redirect vulnerability in Flask-User that enables malicious actors to redirect users to malicious sites by manipulating the URL validation process.

The Impact of CVE-2021-23401

The impact of this CVE is rated as MEDIUM severity with a CVSS base score of 5.4. It requires user interaction and can lead to low confidentiality and integrity impacts.

Technical Details of CVE-2021-23401

Let's explore the technical aspects of CVE-2021-23401 in more detail.

Vulnerability Description

The vulnerability exists in the make_safe_url function of Flask-User, allowing attackers to exploit the flawed URL validation mechanism.

Affected Systems and Versions

All versions of Flask-User are affected by this vulnerability, specifically when using an alternative WSGI server or modifying Werkzeug's default behavior.

Exploitation Mechanism

Attackers can bypass URL validation by inserting multiple backslashes in the URL, redirecting users to arbitrary and potentially malicious sites.

Mitigation and Prevention

Discover how to mitigate the risks associated with CVE-2021-23401.

Immediate Steps to Take

Developers are advised to update Flask-User to a patched version or implement alternative security measures to prevent exploitation.

Long-Term Security Practices

Ensure regular security audits and keep all software components up to date to reduce the risk of such vulnerabilities.

Patching and Updates

Stay informed about security patches and updates for Flask-User to address the Open Redirect vulnerability.