Microsoft Windows is the backbone for millions of devices, but every so often, a sneaky bug puts them at risk. One such flaw is CVE-2022-24485, a vulnerability in the Windows Win32k component that allows remote code execution (RCE) through a file enumeration bug. In this post, we’ll break down what this CVE is, how it works, and walk through some code-level insights, all in straightforward language.

What is CVE-2022-24485?

CVE-2022-24485 is a security vulnerability assigned by MITRE and tracked by Microsoft for Windows systems. The flaw lies in the Win32k.sys driver, which is responsible for core graphical subsystem and input/output operations in Windows. Specifically, this vulnerability lets an attacker abuse the way Windows enumerates files to execute code remotely on the victim's machine.

No user interaction is usually necessary, and the attacker does not require high privileges. That's why this bug is particularly dangerous and received a high severity rating.

Who is Affected?

According to Microsoft’s official advisory, almost all currently supported Windows versions prior to February 2022 were affected:

Windows Server 2022

For the complete affected software list, you can check Microsoft’s bulletin:  
Microsoft Security Update Guide - CVE-2022-24485

The Flaw

The vulnerability is related to how the Win32k.sys device enumerates files and system objects. A flaw in access control allows an attacker to create a scenario where their code is run with higher privileges when a system function tries to enumerate files or directories.

2. A legitimate system process or user action—like the Windows Explorer, triggers enumeration of files in a directory controlled by the attacker.
3. Win32k fails to correctly check permissions or types, causing the system to load the attacker’s malicious file or DLL.

Visual Breakdown

[Attacker's Directory]
    |
    |-- [Malicious DLL/Script]
    |-- [Junction/Symlink -> Windows System Directory]
                     |
                 [System Process]
                        |
         Enumerates Files via Win32k.sys (Unprotected)
                        |
                Loads/Eexecutes Attacker's File

Discovering the Vulnerability

Security researchers analyzing Windows internals found that certain file handling routines in Win32k did not properly verify object types during enumeration. By planting specially crafted reparse points or symbolic links, attackers could trick privileged processes into executing code from locations they controlled.

The original discovery and disclosure were made by experts at Google Project Zero. Here’s their write-up for nerds who want the in-depth technicals:  
Google Project Zero Blog - Windows Win32k Enumeration Vulnerability

Proof-of-Concept Code Snippet

Below is an illustrative (and safe) code snipplet in Python to show how directory junctions can be created on Windows. This is not an actual exploit, but helps you understand the primitive:

import os
import subprocess

# Windows only: create a junction with mklink
def create_junction(source, target):
    cmd = f'mklink /J "{source}" "{target}"'
    subprocess.run(cmd, shell=True)
    print(f"Junction created: {source} -> {target}")

# Demo: simulate a junction in a writable dir to SYSTEM dir
create_junction(r"C:\Temp\attacker_junction", r"C:\Windows\System32")

# The attacker would then drop a payload in C:\Temp\attacker_junction,
# hoping a system process will enumerate here.

Note: Do not use this to cause disruption—this is for educational purposes only.

Public Exploit Details

While Microsoft patched this issue quickly, proof-of-concept and exploit code appeared online soon after. The typical exploit involved:

- Abusing NTFS reparse points / directory junctions

Exploit Pseudo-code

mklink /J C:\Temp\exploitdir C:\Windows\System32
copy attacker.dll C:\Temp\exploitdir\printconfig.dll
sc stop vulnerableService
sc start vulnerableService

How to Protect Yourself

The most important mitigation: Update Windows as soon as possible!  
Windows Update patches Win32k.sys with strict object type checks and removes the vector.

You can read Microsoft’s official update release notes here:  
Microsoft Patch Tuesday - February 2022

References

- Microsoft CVE-2022-24485 Security Update
- Google Project Zero: Technical Write-up
- ZeroDay Initiative - ZDI-22-255

Final Thoughts

CVE-2022-24485 is a perfect example of how a small mistake in core system code can create wide-reaching risks. If you’re a Windows admin or regular user, make sure you apply updates religiously. For defenders, keep an eye on directory manipulation and strange file enumeration patterns—that’s often where attackers slip in.

Timeline

Published on: 04/15/2022 19:15:00 UTC
Last modified on: 04/22/2022 18:23:00 UTC