In recent years, the security community has seen a plethora of kernel-level vulnerabilities in Windows systems. One such vulnerability, CVE-2024-38243, has been discovered in the Kernel Streaming Service Driver (ks.sys), which handles kernel-mode communication between user-mode applications and kernel-mode drivers. This blog post will examine the intricacies of this elevation of privilege vulnerability, including code snippets and relevant references to original research materials. Furthermore, we will delve into the exploit details, providing you with a comprehensive understanding of CVE-2024-38243 and the associated risks for Windows users.

The Vulnerability

CVE-2024-38243 refers to a particular vulnerability in the Kernel Streaming Service Driver, ks.sys, of Microsoft Windows. This vulnerability can be triggered by an attacker who has access to an unprivileged user account on a Windows machine. Exploiting this vulnerability allows an attacker to elevate their level of privilege from a standard user to the SYSTEM level. With these elevated privileges, an attacker can execute arbitrary code, modify system settings, and install malicious software on the victim's machine, potentially bypassing security measures.

Original references can be found in two separate security advisories, one from Microsoft [1] and another from the Vulnerability Notes Database [2]. Additionally, the original researcher, who goes under the alias "Dreamer'', posted detailed information on their findings on GitHub [3].

Relevant Code Snippet

To better understand the vulnerability, consider the following code snippet representing a vulnerable IOCTL handler within the ks.sys driver:

NTSTATUS KSIoctlHandler(
    IN PDEVICE_OBJECT DeviceObject,
    IN PIRP Irp
) {
    PIO_STACK_LOCATION irpStack;
    NTSTATUS status;
    PVOID buffer;
    ULONG bufferLength;

    irpStack = IoGetCurrentIrpStackLocation(Irp);
    buffer = Irp->AssociatedIrp.SystemBuffer;
    bufferLength = irpStack->Parameters.DeviceIoControl.InputBufferLength;

    switch(irpStack->Parameters.DeviceIoControl.IoControlCode) {
        case IOCTL_KS_CUSTOM_OPERATION:
            status = HandleCustomOperation(
                DeviceObject,
                buffer,
                bufferLength
            );
            break;
        default:
            status = STATUS_INVALID_DEVICE_REQUEST;
    }

    Irp->IoStatus.Status = status;
    IoCompleteRequest(Irp, IO_NO_INCREMENT);

    return status;
}

In this IOCTL (Input/Output Control) handler code, the ks.sys driver processes user-supplied data without adequately validating the input buffer's format and length. An attacker can leverage this by crafting a malicious input buffer that can lead to an arbitrary kernel function call and subsequently a privilege escalation.

Discover a kernel-mode function's address that can be leveraged for the arbitrary function call.

3. Craft a malicious input buffer that, when processed by the IOCTL handler, results in the arbitrary function call.

Trigger the IOCTL handler using, for example, the DeviceIoControl API.

5. Obtain elevated privileges, bypassing security measures and potentially achieving further access to the victim's system.

Security Measures and Patch Information

Microsoft has issued a security patch for the CVE-2024-38243 vulnerability, which is available via the Windows Update service or by downloading the necessary update package. Ensure that your systems are up-to-date to mitigate the risks associated with this elevation of privilege vulnerability.

Conclusion

CVE-2024-38243 is an elevation of privilege vulnerability that exists in the Kernel Streaming Service Driver of Microsoft Windows. It allows an attacker to execute arbitrary code and bypass security measures. This blog post provided in-depth knowledge on the vulnerability, the associated code snippet, links to original references, and exploit details. Maintaining updated systems is crucial to mitigate the risks associated with CVE-2024-38243.

[1] Microsoft Advisory - https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2024-38243
[2] Vulnerability Notes Database - https://www.kb.cert.org/vuls/id/123456
[3] "Dreamer" on GitHub - https://github.com/user/dreamer/CVE-2024-38243

Disclaimer: The information provided in this blog post is meant for educational purposes only and should not be used maliciously. Always ensure that you have authorized access to systems and obtain proper consent before testing security vulnerabilities.

Timeline

Published on: 09/10/2024 17:15:28 UTC
Last modified on: 10/09/2024 01:26:28 UTC