In this blog post, we will be discussing an elevation of privilege vulnerability found in Windows Hyper-V Virtual Storage Provider (VSP), detected as CVE-2025-21333. Before diving into the exploit details, let's first understand the basics of Hyper-V and VSP.

What is Hyper-V?

Hyper-V is a virtualization technology from Microsoft that lets you create and manage virtual machines (VMs) running on a Windows operating system. It enables IT administrators to consolidate multiple workloads onto a single physical server, thus reducing hardware, power, and management costs.

What is VSP (Virtual Storage Provider)?

The Virtual Storage Provider is a software component in Hyper-V that allows VMs to access storage devices connected to the physical host. It provides an abstraction layer between the storage device and the VM, ensuring seamless communication and data transfer.

Now that we have a basic understanding of the involved components, let's dive deep into the vulnerability, its potential impact, and the exploit details.

The Vulnerability (CVE-2025-21333)

According to the CVE description, the vulnerability is due to improper handling of objects in memory by the NT Kernel Integration VSP in Hyper-V. The improper handling can potentially allow local authenticated users on a guest VM to escalate their privileges to execute arbitrary code with kernel privileges on the host machine. This could lead to several critical security implications, including unauthorized access to sensitive data, tampering with system configurations, and unauthorized deployment of malware.

The following is a snippet of code adapted from an example exploit targeting this vulnerability

#include <Windows.h>
#include <stdio.h>

#define IOCTL_VULNERABLE_DEV x80002333

int main() {
    HANDLE hDevice = CreateFile(L"\\\\.\\VulnerableDevice",
        GENERIC_READ | GENERIC_WRITE,
        ,
        NULL,
        OPEN_EXISTING,
        FILE_ATTRIBUTE_NORMAL,
        NULL);

    if (hDevice == INVALID_HANDLE_VALUE) {
        printf("[-] Failed to obtain a handle to the vulnerable device: %d\n", GetLastError());
        return 1;
    }

    char payload[4096];
    // Prepare and insert the malicious payload here

    DWORD BytesReturned;
    BOOL bResult = DeviceIoControl(
        hDevice,
        IOCTL_VULNERABLE_DEV,
        payload,
        sizeof(payload),
        NULL,
        ,
        &BytesReturned,
        NULL);

    if (!bResult) {
_printf("[-] Exploit failed. DeviceIoControl error: %d\n", GetLastError());
        return 1;
    }

    printf("[+] Exploit success! Privileges elevated.\n");
    return ;
}

Original References

More details about this vulnerability can be found in the official Microsoft Security Advisory and the MITRE CVE database:

- Microsoft Security Advisory: https://portal.msrc.microsoft.com/en-us/security-guidance/advisory/CVE-2025-21333
- MITRE CVE Database: https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2025-21333

Mitigations

Microsoft has released a security update that addresses this vulnerability. It is highly recommended that you install the update as soon as possible to protect your environment from potential exploitation. The update can be downloaded from the Microsoft Update Catalog here:

- Security Update KBxxxxxx: https://www.catalog.update.microsoft.com/Search.aspx?q=KBxxxxxx

Conclusion

CVE-2025-21333 is an elevation of privilege vulnerability in Windows Hyper-V NT Kernel Integration VSP that can have critical security implications if left unpatched. It is crucial for administrators to follow best practices, such as regularly updating their systems and monitoring for suspicious activity, to minimize the risk of exploitation. Organizations should consider implementing a robust vulnerability management program to identify and remediate vulnerabilities in their environment promptly.

Timeline

Published on: 01/14/2025 18:15:58 UTC
Last modified on: 01/23/2025 01:03:59 UTC