*Published: June 2024*


*In this post, we dig deep into CVE-2024-49077—a newly reported security flaw in Windows affecting millions of laptops and devices with mobile broadband connectivity. We break down what this vulnerability means, how an attacker might exploit it, and what you can do to stay safe. The goal is to keep things simple, clear, and helpful, even if you aren’t a security expert.*

What is CVE-2024-49077?

CVE-2024-49077 is an Elevation of Privilege (EoP) bug found in the Windows Mobile Broadband Driver. In short: someone with low-level access to your Windows PC (like a regular user or an attacker running code with your permissions) can trick the system into giving them much higher privileges—possibly SYSTEM level access.

Microsoft addressed this issue as part of their June 2024 Patch Tuesday release. If left unpatched, it might allow malware or bad actors to take full control of affected Windows devices.

Windows Server (all supported versions)

You’re vulnerable if you use a laptop or PC with a built-in mobile broadband adapter, or USB dongles for 4G/5G internet. The bad driver is enabled by default on a surprising number of enterprise laptops!

It works through a core Windows driver, usually called mbn_msflt.sys.

- The bug: an attacker can send a carefully crafted request to the driver. The driver fails to check permissions correctly and runs the attacker’s code at higher privilege.

In practical terms:
A non-admin user or a process running as a regular user can execute code and get SYSTEM privileges—meaning they could install software, access sensitive data, or even disable security tools.

Attack Scenario

1. Local Access Needed: The attacker must already have some access (local user, maybe via phishing or a malicious app).

Malicious Code: The attacker runs a specially crafted program on the target system.

3. Trigger the Driver Bug: The program sends specific, malformed data to the Windows Mobile Broadband API, which is then processed by mbn_msflt.sys.
4. Privilege Escalation: Because the driver doesn’t check permissions right, it executes code provided by the attacker at SYSTEM level.

Proof of Concept: Code Snippet

Below is a *simplified and safe* code snippet that demonstrates how an exploit might interact with the vulnerable driver. (This is for educational purposes only!)

// Windows API: Open a handle to the Mobile Broadband device
HANDLE hDevice = CreateFile(
    L"\\\\.\\mbn_msflt",      // Mobile broadband filter device
    GENERIC_READ | GENERIC_WRITE,
    ,
    NULL,
    OPEN_EXISTING,
    FILE_ATTRIBUTE_NORMAL,
    NULL);

if (hDevice == INVALID_HANDLE_VALUE) {
    printf("Could not open device: %ld\n", GetLastError());
    return 1;
}

// Send malicious IOCTL to trigger the vulnerability
DWORD bytesReturned;
BYTE payload[256] = {}; // Malcrafted payload
BOOL result = DeviceIoControl(
    hDevice,
    IOCTL_CODE_FOR_BUG,     // Hypothetical IOCTL code that triggers the bug
    payload,
    sizeof(payload),
    NULL,
    ,
    &bytesReturned,
    NULL);

if (!result) {
    printf("Exploit failed: %ld\n", GetLastError());
} else {
    printf("Exploit attempt sent. Check if privileges increased.\n");
}

CloseHandle(hDevice);

Note: For safety and legality, we do not share actual payloads or full exploit code.

Real-World Risk

- Enterprise Devices: Many business laptops have mobile broadband drivers enabled even if not used—a golden target for attackers.
- Malware: Ransomware or Trojans can quickly take advantage once they’re in your system as a standard user.
- Persistence: Attackers could use SYSTEM access to create new admin accounts, install rootkits, or wipe logs to cover their tracks.

Microsoft released a fix in their June 2024 cumulative updates.

Microsoft Security Guide

Monitor for Signs of PrivEsc:

Look for unknown user accounts, unauthorized administrative activities, or tools like PsExec running.

Enterprise Admins—Deploy Patches via WSUS or SCCM:

See Microsoft guidance

References

- Microsoft CVE-2024-49077 Security Advisory
- Mitre CVE Database - CVE-2024-49077
- Windows Mobile Broadband Overview

Final Thoughts

CVE-2024-49077 is a textbook example of why driver vulnerabilities are so dangerous: they work below the radar and can give attackers control over the entire system. If you or your company use Windows devices with mobile broadband, patch as soon as possible! Always check what hardware and drivers you’re running—and lock down what you don’t need.

Timeline

Published on: 12/12/2024 02:04:31 UTC
Last modified on: 12/20/2024 07:44:49 UTC