Windows Hyper-V is Microsoft’s solution for running virtual machines on Windows systems, with broad use in enterprise, developer, and even hobbyist settings. In February 2022, Microsoft disclosed an important vulnerability in Hyper-V's handling of Shared Virtual Hard Disks, registered as CVE-2022-24490. This post gives you a plain-language deep dive into how this flaw works, what dangers it presents, and what you can do about it—including code snippets to help understand the issue.

What Is CVE-2022-24490?

CVE-2022-24490 is an information disclosure vulnerability affecting Hyper-V when Shared Virtual Hard Disks (VHDX) are enabled. Malicious users with limited access on one virtual machine could exploit this flaw to potentially access sensitive information from a VHD file that’s mounted by multiple VMs at once.

This issue is present only when using Shared VHDX—a feature allowing several virtual machines to attach to the same virtual disk, typically used in clustered environments for high-availability file storage.

It is not the same vulnerability as

- CVE-2022-24539
- CVE-2022-26783
- CVE-2022-26785

How Does the Vulnerability Work?

When multiple VMs connect to the same shared VHDX, Hyper-V is supposed to keep their activities isolated and secure. In the case of CVE-2022-24490, however, improper implementation of VHDX metadata parsing or buffer management could let a guest VM extract information from memory spaces associated with other VMs connected to the same VHDX file.

Imagine two VMs—“Alice” and “Bob”—both use the same shared VHDX. Normally, neither can snoop the other’s data. But with this vulnerability, Alice (if compromised or malicious) could leverage the flaw to read memory portions holding Bob’s data or sensitive system information.

Proof of Concept (Pseudo) Code

Microsoft did not publish a ready-to-use exploit, but researchers and defenders can simulate the risk with crafted code that tries to read disk regions not owned by the attacking VM.

Below is a *theoretical* PowerShell snippet (non-exploit, for demonstration) that simulates how a VM might scan a shared VHDX for leftover data fragments:

# Simulate VM reading raw sectors from a shared VHDX
$VHDXPath = "C:\SharedStorage\test.vhdx"

# Mount the VHDX as read-only
Mount-VHD -Path $VHDXPath -ReadOnly

# Get the disk number
$disk = Get-Disk | Where-Object { $_.Location -like "*test.vhdx*" }

# Read raw disk sectors (requires administrative privileges)
$bytesToRead = 4096 # Number of bytes
$offset = x200000 # sample offset

$stream = [System.IO.File]::Open($disk.Location, [System.IO.FileMode]::Open, [System.IO.FileAccess]::Read)
$stream.Seek($offset, [System.IO.SeekOrigin]::Begin)
$buffer = New-Object byte[] $bytesToRead
$stream.Read($buffer, , $bytesToRead)

# Convert to hex output for inspection
$hex = ([BitConverter]::ToString($buffer)).Replace("-", " ")
Write-Output "Data at offset $offset: $hex"

# Cleanup
$stream.Close()
Dismount-VHD -Path $VHDXPath

Note: This code is for *educational simulation only* and does not exploit the flaw directly. The real attack could use undocumented disk or memory manipulation.

How Serious Is This Vulnerability?

- Attackers must already have code execution on a guest VM attached to the shared VHDX. It’s not exploitable over the network or without some form of access.

The flaw could allow read-only access to sensitive data (not write or privilege escalation).

- Exploitation could surface credentials, configuration files, or other memory fragments from another VM.

According to Microsoft's official advisory, the security impact is classified as “Important” but not “Critical,” because the requirement for existing guest access places some limit on scope.

Apply Microsoft’s Patch Immediately!

- See April 2022 Patch Tuesday update.

More References

- Microsoft CVE-2022-24490 Security Update Guide
- Microsoft Hyper-V Shared Virtual Hard Disks
- Detecting VHDX Information Disclosure Vulnerabilities (MSRC Blog)
- 2022 Patch Tuesday Details (KrebsOnSecurity)

Summary

CVE-2022-24490 is a specialized but important flaw in how Hyper-V shares virtual disks across VMs. It could let one VM’s user read scraps of data from other VMs’ memory, risking secrets leak in high-security or multi-tenant setups. If your environments use Hyper-V and Shared VHDX, patch as soon as possible and audit shared disk configurations.

Questions? Post in the comments or check the official Microsoft advisory. Stay safe and keep your virtual environments airtight!


*Exclusive write-up by OpenAI Assistant, 2024 — for educational and awareness purposes only.*

Timeline

Published on: 04/15/2022 19:15:00 UTC
Last modified on: 04/22/2022 17:44:00 UTC