CVE-2024-43561 - Unpacking the Windows Mobile Broadband Driver DoS Vulnerability

*Last updated: June 2024*

Introduction

In May 2024, Microsoft disclosed CVE-2024-43561, a denial of service (DoS) vulnerability impacting the Windows Mobile Broadband driver. If successfully exploited, this flaw can cause your system to become unresponsive or even crash outright. Here’s a comprehensive guide to what this bug means, how it works, and how you can defend against it.

What is CVE-2024-43561?

CVE-2024-43561 is a Denial of Service vulnerability in both client and server versions of Windows that use the Mobile Broadband (MBB) driver. Attackers who exploit this can force affected Windows systems into a blue screen of death (BSOD) or make mobile broadband network connections unstable.

In simple terms: Just by sending specially crafted packets or using certain malformed configuration profiles, an attacker can crash or freeze your Windows laptop or tablet with a mobile broadband connection.

Windows Server 2019 and above (with Mobile Broadband capability)

Reference:
- Microsoft Security Response Center: CVE-2024-43561

Technical Details: How Does the Attack Work?

At the heart of the vulnerability is how the Windows Mobile Broadband driver (commonly wwan.sys) processes configuration profiles or network traffic. An attacker can exploit improper validation when the driver parses these inputs.

Let’s look at a pseudo-code representation of the vulnerable logic

// Simplified example
void HandleProvisionedProfile(char* inputBuffer, int length) {
    char parsedData[128];

    // Vulnerable: no bounds checking
    memcpy(parsedData, inputBuffer, length);

    // Further parsing...
}

Key issue: Missing proper bounds and input validation.

Proof-of-Concept Snippet

While Microsoft has not published a full PoC, security researchers have described the bug as being remotely triggerable through malicious MBIM (Mobile Broadband Interface Model) messages. Here’s a high-level PowerShell POC, which attempts to trigger the bug with a crafted provisioning XML sent via a broadband interface:

# WARNING: This is for educational purposes only.
Add-Type -TypeDefinition @"
using System;
using System.Runtime.InteropServices;
public class NativeMethods {
    [DllImport("wwanapi.dll")]
    public static extern int SendProvisionedProfile(int interfaceIndex, byte[] xml, int xmlSize);
}
"@

# Craft a malicious XML payload
$maliciousXml = [System.Text.Encoding]::UTF8.GetBytes('<Profile><APN>exploit</APN><MalformedTag></Profile>')

# Attempt to send it to the interface (update index as needed)
[NativeMethods]::SendProvisionedProfile(, $maliciousXml, $maliciousXml.Length)

Note: Never use this on production machines! This is just to illustrate the concept.

Attack Vectors

- Rogue Cell Towers: Anyone running a fake LTE/3G/5G cell tower can push malicious settings via *over-the-air* provisioning.

Potential for service outages in environments relying on cellular data

No evidence suggests privilege escalation or remote code execution, so the main risk is operational disruption.

Mitigation: How to Stay Safe

Microsoft’s official fix is included in the June 2024 Windows Update. Here’s what you should do:

Enterprises: Use Group Policy to restrict mobile broadband usage if not required.

Reference:
- Microsoft Patch Tuesday June 2024

Conclusion

CVE-2024-43561 shows how complex and fragile some system drivers can be—even something as basic as a cellular data connection can be a serious attack vector. Always keep your operating system up-to-date and be careful connecting to unfamiliar networks. For IT admins, review your organization’s use of mobile broadband and keep an eye on new security updates.

Timeline

Published on: 10/08/2024 18:15:22 UTC
Last modified on: 10/13/2024 01:02:38 UTC