Hayden

If you’re running Windows systems, you need to know about the recently discovered CVE-2025-55226 Graphics Kernel vulnerability. This vulnerability affects the core graphics processing components of Windows and could put your entire system at risk if exploited. Fortunately, Microsoft has already released a fix, and this guide will walk you through the cause and resolution methods in detail.

 

 

1. What is CVE-2025-55226?

CVE-2025-55226 is a race condition vulnerability discovered in the Windows Graphics Kernel. This vulnerability was disclosed during Microsoft’s September 2025 Patch Tuesday and is classified as Critical with a CVSS score of 6.7.

What is a Race Condition? A race condition occurs when multiple processes or threads access the same resource simultaneously. Think of it like two people trying to open the same door at exactly the same time – conflicts are bound to happen.

Key characteristics of this vulnerability:

  • Affected Systems: Windows 10, Windows 11, Windows Server 2019, 2022, 2025
  • Exploitation Requirements: Authenticated local user privileges required
  • Attack Complexity: High (must win the race condition)
  • User Interaction: Required (executing malicious files, etc.)

 

 

2. What Are the Risks? Impact Analysis

When exploited, this vulnerability can lead to severe consequences:

Kernel-Level Privilege Escalation

Attackers can execute code in kernel context, gaining complete control over the system. This means:

  • Rootkit Installation: Covertly installing malware deep within the system
  • Security Solution Bypass: Disabling antivirus, firewalls, and other security programs
  • Data Theft: Accessing all files and information on the system
  • Persistent Access: Maintaining attack infrastructure that survives system reboots

High-Risk Environments

Terminal servers, shared desktops, VDI hosting environments, developer/lab machines, and multi-user server scenarios face the greatest risk.

 

 

3. How Does the Attack Work? Understanding Attack Scenarios

Step-by-Step Attack Process

Stage 1: Initial Access

  • Attacker first needs local account access to the system
  • Social engineering to trick users into executing malicious files
  • Phishing emails with malicious attachments or links

Stage 2: Triggering Race Condition

  • Attacker induces concurrent access to graphics subsystem resources
  • Manipulates shared kernel resources without proper synchronization
  • Coordinates multiple threads to access the same graphics resources simultaneously

Stage 3: Kernel Privilege Acquisition

  • Winning the race condition corrupts kernel state
  • Enables arbitrary code execution in kernel mode

 

 

4. How to Check If Your System Is Vulnerable

Checking Windows Version

Press Windows Key + R to open the Run dialog and type winver.

The following versions are vulnerable:

  • Windows 10 (all versions)
  • Windows 11 (all versions)
  • Windows Server 2019, 2022, 2025

Checking Installed Updates

  1. Go to Settings → Update & Security → Windows Update
  2. Click View update history
  3. Check if the following KB numbers are installed:
    • Windows 11 24H2: KB5065426
    • Windows 11 23H2: KB5065431
    • Windows 10: KB5065429
    • Windows Server 2025: KB5065426
    • Windows Server 2022 (21H2/22H2): KB5065432
    • Windows Server 2022 23H2: KB5065425
    • Windows Server 2019: KB5065427
    • Windows Server 2016: KB5065427

PowerShell Verification Method

Run PowerShell as administrator and execute:

Get-HotFix | Where-Object {$_.HotFixID -match "KB5065426|KB5065431|KB5065429|KB5065432|KB5065425|KB5065427"}

 

 

5. Patch Installation Methods – Step-by-Step Guide

Automatic Updates (Recommended)

Windows 11 Users

  1. Open Settings app (Windows Key + I)
  2. Select Windows Update
  3. Click Check for updates
  4. Click Download and install
  5. After installation completes, click Restart now

Windows 10 Users

  1. Settings → Update & Security
  2. Windows Update → Check for updates
  3. KB5065429 will download and install automatically
  4. Proceed with restart

Manual Download and Installation

Download directly from Microsoft Update Catalog:

  1. Visit Microsoft Update Catalog
  2. Search for the appropriate KB number:
    • Windows 11 24H2: KB5065426
    • Windows 11 23H2: KB5065431
    • Windows 10: KB5065429
    • Windows Server 2025: KB5065426
    • Windows Server 2022 (21H2/22H2): KB5065432
    • Windows Server 2022 23H2: KB5065425
    • Windows Server 2019: KB5065427
    • Windows Server 2016: KB5065427
  3. Download the file matching your system architecture (x64, x86, ARM64)
  4. Double-click the downloaded .msu file to install

Enterprise Patch Management

Using WSUS (Windows Server Update Services)

  1. In WSUS Admin Console, go to Updates → All Updates
  2. Approve CVE-2025-55226 related updates
  3. Deploy to client computers

Using SCCM (System Center Configuration Manager)

  1. Software Library → Software Updates
  2. Create update packages and deployment groups
  3. Establish phased deployment plan

 

 

6. Windows Server Patch Management

Server-Specific KB Numbers and Installation

Windows Server 2025

  • KB Number: KB5065426
  • Installation: Same process as Windows 11 24H2

Windows Server 2022

Windows Server 2019

  • KB Number: KB5065427
  • Shared with Windows 10 2016 LTSC

Windows Server 2016

  • KB Number: KB5065427
  • Available through Windows Update and WSUS

Server Core Installation

For Windows Server Core installations without GUI:

Check Current Version

Get-ComputerInfo | Select-Object WindowsProductName, WindowsVersion, TotalPhysicalMemory

Install Updates via PowerShell

# Install PSWindowsUpdate module if not present
Install-Module PSWindowsUpdate -Force

# Check for available updates
Get-WUList

# Install specific KB update
Install-WindowsUpdate -KBArticleID "KB5065432" -AcceptAll -AutoReboot

Manual Installation for Server Core

# Download and install via DISM
dism /online /add-package /packagepath:"C:\temp\KB5065432.msu"

Cluster Environment Patching

For Failover Clusters

  1. Prepare cluster nodes: Ensure all nodes are healthy
  2. Pause cluster node: Suspend-ClusterNode -Name NodeName
  3. Apply patches: Install KB updates on paused node
  4. Resume and failover: Resume-ClusterNode -Name NodeName
  5. Repeat for remaining nodes: One node at a time

Using Cluster-Aware Updating (CAU)

# Enable CAU if not configured
Add-CauClusterRole -ClusterName "YourClusterName" -MaxFailedNodes 1

# Run CAU scan
Invoke-CauScan -ClusterName "YourClusterName"

# Apply updates
Invoke-CauRun -ClusterName "YourClusterName" -Force

Hyper-V Host Considerations

Live Migration Prerequisites

  • Ensure all Hyper-V hosts in the cluster are patched
  • Plan VM migrations during maintenance windows
  • Verify sufficient resources on target hosts

Minimal Downtime Strategy

  1. Live migrate VMs from host to be patched
  2. Apply security updates
  3. Restart host if required
  4. Migrate VMs back after verification

 

 

7. Post-Patch Verification

Confirming Update Installation

After applying the patch, verify installation using these methods:

Method 1: System Information Check

  1. Windows Key + R → type msinfo32
  2. Check OS version in System Summary
  3. Verify latest build number is displayed

Method 2: Event Log Check

  1. Run Event Viewer
  2. Windows Logs → System
  3. Check for installation-related Event IDs 43, 44

System Stability Check

After patch installation, verify the following:

  • Graphics Performance: Ensure games and graphics-intensive applications work normally
  • Driver Compatibility: Verify GPU drivers function properly
  • Applications: Check that frequently used programs operate correctly

 

 

8. Additional Security Hardening

System-Level Security Enhancement

Enable Virtualization-based Security (VBS)

  1. Run Group Policy Editor (gpedit.msc)
  2. Computer Configuration → Administrative Templates → System → Device Guard
  3. Enable Turn On Virtualization Based Security policy

Enable Hypervisor-protected Code Integrity (HVCI)

  1. Open Windows Security app
  2. Device Security → Core Isolation
  3. Enable Memory Integrity

Network Security Configuration

Enable SMB Signing (Additional security for CVE-2025-55234)

# Run in PowerShell as administrator
Set-SmbServerConfiguration -RequireSecuritySignature $true -Force
Set-SmbClientConfiguration -RequireSecuritySignature $true -Force

 

 

9. Troubleshooting Guide

Patch Installation Failure Solutions

Error Code Solutions

Error Code Cause Solution
0x80070020 File in use Retry in Safe Mode
0x8007000D Corrupted download Clear cache folder and re-download
0x80240017 Service issue Restart Windows Update service

Run Windows Update Troubleshooter

  1. Settings → Update & Security → Troubleshoot
  2. Run Windows Update troubleshooter
  3. Apply automatic diagnosis and fixes

Compatibility Issue Resolution

Graphics Driver Updates

Application Compatibility For problematic applications:

  1. Try running in compatibility mode
  2. Update to latest version
  3. Contact manufacturer for compatibility patches

 

 

CVE-2025-55226 is a critical security vulnerability affecting Windows’ core graphics processing components. Microsoft provided a solution through the September 2025 Patch Tuesday, and applying these updates is the most reliable security measure.

Enterprise environments should implement phased patching to ensure stability while maintaining rapid security updates. Individual users should enable automatic updates to avoid missing critical security patches like this one.

Security isn’t a one-time patch application. Maintain a safe IT environment through continuous monitoring and updates.

 

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