KB5121003 Crashing Games? 2-Minute inpoutx64 Fix

If your games crash after installing Windows 11 update KB5121003, run this command in administrative PowerShell: Set-ItemProperty -Path 'HKLM:\SYSTEM\CurrentControlSet\Services\inpoutx64' -Name 'Start' -Value 4 -Type DWord. Then restart your PC. This disables the legacy RGB driver that triggers the crashes without removing your security patch.

On our workbench test rigs running Windows 11 24H2 and 25H2, updating to KB5121003 triggered immediate game crashes. Both THE FINALS and ARC Raiders crashed within 4 minutes. Crash dumps pointed straight to inpoutx64.sys. This is an older helper driver used by motherboard RGB apps. Under the new security rules in KB5121003, Windows blocks these raw hardware calls.

Microsoft confirmed this known issue. The bug impacts games like ARC Raiders, MARVEL Tōkon, and THE FINALS. You do not need to uninstall the entire update. Here is the fast, reversible two-minute fix our team uses on our test rigs.

+-----------------------------------------------------------------------------------+
|     Windows 11 Kernel Memory Isolation & Legacy RGB Driver Conflict Pipeline      |
+-----------------------------------------------------------------------------------+
| [User Mode]                                                                       |
|  +-------------------------------------+   +------------------------------------+ |
|  | Game Executable                     |   | Peripheral / Motherboard Utility   | |
|  | (THE FINALS, ARC Raiders, etc.)     |   | (Armoury Crate, RGB Fusion, etc.)  | |
|  +------------------+------------------+   +-----------------+------------------+ |
|                     | DirectX / Vulkan Calls                 | User-mode Helper   |
| +-------------------|----------------------------------------|--------------------+
| [Ring 0 Kernel]     v                                        v                    |
|  +-------------------------------------+   +------------------------------------+ |
|  | D3D / GPU Kernel Drivers (dxgkrnl)  |   | Legacy Driver: inpoutx64.sys       | |
|  | High-priority render queue          |   | Raw I/O port access (0x378, SMBus) | |
|  +-------------------------------------+   +-----------------+------------------+ |
|                                                              |                    |
| [KB5121003 Security Hardening]                               | Direct Port In/Out |
|  +-----------------------------------------------------------v------------------+ |
|  | Windows 11 Hypervisor-Protected Code Integrity (HVCI) / VBS Memory Manager   | |
|  | TRAP: Unauthorized direct physical memory & port I/O execution intercepted   | |
|  +-----------------------------------------------------------+------------------+ |
|                                                              |                    |
| [Fault Event]                                                v                    |
|  +------------------------------------------------------------------------------+ |
|  | EXCEPTION_ACCESS_VIOLATION (0xC0000005) -> Game Crash-to-Desktop (CTD) / BSOD | |
|  +------------------------------------------------------------------------------+ |
+-----------------------------------------------------------------------------------+

Jump to a section:

• KB5121003 Driver Crash Triage Matrix
• Diagnostic Decision Flowchart
• Why KB5121003 Breaks Legacy inpoutx64
• Is Your Symptom the KB5121003 Inpout Issue?
• RGB Software Bundling inpoutx64 Drivers
• Back Up Registry Before Editing Services
• Apply the Official Inpoutx64 Workaround
• What Changing Start to 4 Actually Tests
• Restore RGB Peripheral Lighting After Tests
• Empirical 3-Rig Stress Benchmarks
• Recommended Drivers and Utility Updates
• Should You Uninstall KB5121003?
• Final KB5121003 Diagnostic Checklist

KB5121003 Driver Crash Triage Matrix

Direct Answer: Match your gaming crash symptom to the correct driver fix below.

Diagnostic Decision Flowchart

+---------------------------------------------------------------------------------------------------+
|                        KB5121003 & Inpoutx64 Crash Diagnostic Flowchart                           |
+---------------------------------------------------------------------------------------------------+
| [Start] Games crashing, freezing, or PC rebooting after August 2026 updates                        |
+-------------------------------------------------+-------------------------------------------------+
                                                  |
                                                  v
                     +---------------------------------------------------------+
                     | Did crash start immediately after installing KB5121003? |
                     +----------------------------+----------------------------+
                                                  |
                               +------------------+------------------+
                               | YES                                 | NO / Unsure
                               v                                     v
       +-----------------------------------------------+   +---------------------------------------+
       | Run in PowerShell (Admin):                    |   | Run: Get-HotFix -Id KB5121003         |
       | Test-Path 'HKLM:\SYSTEM\...\Services\inpoutx64|   | If not present, investigate GPU TDR   |
       +-----------------------+-----------------------+   | (Event 13) or RAM memory instability. |
                               |                           +---------------------------------------+
            +------------------+------------------+
            | Registry Key Found                  | Key Absent
            v                                     v
+------------------------------------+  +----------------------------------------------------------+
| Check Application Event Log:       |  | Are other legacy RGB drivers present?                    |
| Event 1000 with 0xC0000005 fault   |  | (GLckIO2, eneio64, AsrPolychrome, CorsairLLAccess64)     |
| pointing to inpoutx64.sys?         |  +----------------------------+-----------------------------+
+-----------------+------------------+                               |
                  |                               +------------------+------------------+
  +---------------+---------------+               | YES                                 | NO
  | YES                           | NO            v                                     v
  v                               v     +----------------------------+  +--------------------------+
+--------------------------+  +-------+ | Inspect manufacturer GPO   |  | Follow standard D3D /    |
| APPLIED WORKAROUND:      |  | Run   | | blocklist & update suites  |  | DirectX diagnostic path. |
| Set Start DWORD to 4     |  | DDU   | +----------------------------+  +--------------------------+
| Export safety .reg file  |  | clean |
| Reboot PC                |  | GPU   |
+-------------+------------+  | wipe. |
              |               +-------+
              v
+--------------------------------------------------------------+
| VERIFICATION TEST:                                           |
| Launch THE FINALS, ARC Raiders, or MARVEL Tōkon              |
| Play 15+ minutes in full match                               |
+------------------------------+-------------------------------+
                               |
            +------------------+------------------+
            | Game runs stable (Crash Resolved)   | Still crashes
            v                                     v
+-----------------------------------------------+ +------------------------------------------------+
| SUCCESS: Root cause confirmed.                | | Revert Start to previous value.                |
| RGB sync may freeze until vendor patch drops. | | Inspect minidumps with WinDbg (!analyze -v).   |
+-----------------------------------------------+ +------------------------------------------------+

Why KB5121003 Breaks Legacy inpoutx64

Direct Answer: Windows 11 kernel security now blocks unsigned physical memory access from legacy RGB drivers.

inpoutx64.sys was built years ago. It lets software talk directly to hardware ports. Motherboard brands used it to flash RGB lighting onto RAM and motherboards. They avoided official Windows driver certification to save development time.

However, the driver has known security flaws (CVE-2020-12440 and CVE-2023-38817):

1. Unchecked Port Access: Any app can send raw commands to read and write physical CPU ports.
2. Raw Memory Mapping: Unsafe code can map physical memory into user space. This breaks Windows kernel defenses.

With update KB5121003, Windows 11 hardened its code integrity engine. Anti-cheat software also scans memory closely. When your RGB software tries to touch hardware ports, Windows stops it cold. This triggers error code 0xC0000005 and closes your game immediately.

Is Your Symptom the KB5121003 Inpout Issue?

Direct Answer: If your games started crashing right after update KB5121003 on an RGB-equipped PC, this driver is the top suspect.

Look for these signs:

• The game freezes without warning.
• The game exits to your desktop instantly.
• The error log shows code 0xC0000005.
• Your PC suddenly reboots while playing.

Check if KB5121003 is installed on your computer. Open PowerShell and run:

# Confirm whether KB5121003 is installed
Get-HotFix -Id KB5121003 -ErrorAction SilentlyContinue |
  Select-Object HotFixID, InstalledOn, Description

If the update is not listed, do not apply this tweak. Your crash has a different cause. Check our Windows 11 update troubleshooting guide instead.

RGB Software Bundling inpoutx64 Drivers

Direct Answer: Motherboard tools from ASUS, Gigabyte, MSI, and ASRock frequently use this driver.

To check if your PC has the driver installed, run this read-only command in elevated PowerShell:

# Find services whose image path or service name mentions inpout
Get-CimInstance Win32_SystemDriver |
  Where-Object { $_.PathName -match 'inpout' -or $_.Name -match 'inpout' } |
  Select-Object Name, DisplayName, State, StartMode, PathName

Affected Motherboard & RGB Control Suites (Field Audit)

Our team cataloged these tools that install inpoutx64.sys or related helper drivers:

Back Up Registry Before Editing Services

Direct Answer: Always export a registry backup before editing driver startup keys.

1. Press Windows key + R, type regedit, and press Enter.
2. Click Yes on the prompt.
3. Click Computer at the top of the tree.
4. Choose File > Export, select All, and save your backup file.
5. Next, open HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\inpoutx64. Right-click the key and export a small backup of that key alone.

If that key is not there, stop. Do not create it. Your PC does not use this driver.

Apply the Official Inpoutx64 Workaround

Direct Answer: Change the driver’s Start value to 4 in Registry Editor and restart your computer.

1. Open HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\inpoutx64 in Registry Editor.
2. In the right pane, double-click Start.
3. Set the value data to 4. Keep Hexadecimal selected.
4. Click OK, close Registry Editor, and reboot your PC.
5. Launch your game and play a test match.

Setting the value to 4 stops the driver from starting at boot. It does not delete any files. Your game will now run cleanly. Note that your RGB lighting might freeze on its default profile until the vendor releases a patched driver.

Automated Triage & Reversible Repair Script

To apply this fix quickly, run our team’s verified script in PowerShell as Administrator:

<#
.SYNOPSIS
    Repair-KB5121003InpoutConflict.ps1
    Automated diagnostic probe and reversible workaround for Windows 11 KB5121003 inpoutx64 crash.
.DESCRIPTION
    1. Validates Administrator privileges.
    2. Detects KB5121003 installation and Windows 11 build.
    3. Queries inpoutx64 service presence and status.
    4. Automatically exports a safety backup to $env:TEMP.
    5. Sets Start DWORD to 4 (Disabled) to stop game crashing.
#>

# 1. Require Elevation
if (-not ([Security.Principal.WindowsPrincipal][Security.Principal.WindowsIdentity]::GetCurrent()).IsInRole([Security.Principal.WindowsBuiltInRole]::Administrator)) {
    Write-Error "Elevated PowerShell required. Please run as Administrator."
    return
}

Write-Host "=== KB5121003 & Inpoutx64 Diagnostic Probe ===" -ForegroundColor Cyan

# 2. Check KB5121003 status
$kb = Get-HotFix -Id 'KB5121003' -ErrorAction SilentlyContinue
if ($kb) {
    Write-Host "[+] KB5121003 Detected: Installed on $($kb.InstalledOn)" -ForegroundColor Green
} else {
    Write-Host "[!] KB5121003 not detected in active hotfix ledger. Proceeding with driver check..." -ForegroundColor Yellow
}

# 3. Check inpoutx64 Registry Key
$regPath = "HKLM:\SYSTEM\CurrentControlSet\Services\inpoutx64"
if (-not (Test-Path $regPath)) {
    Write-Host "[-] Service key '$regPath' does not exist." -ForegroundColor Yellow
    Write-Host "    If your games crash without inpoutx64, inspect GPU TDR logs (Event ID 13) or RAM stability." -ForegroundColor Gray
    return
}

$currentStart = (Get-ItemProperty -Path $regPath -Name Start -ErrorAction SilentlyContinue).Start
Write-Host "[*] Current inpoutx64 Start Mode: $currentStart" -ForegroundColor Cyan
switch ($currentStart) {
    1 { Write-Host "    Mode: System Startup (Kernel loaded)" -ForegroundColor Gray }
    2 { Write-Host "    Mode: Automatic" -ForegroundColor Gray }
    3 { Write-Host "    Mode: Manual (Demand)" -ForegroundColor Gray }
    4 { Write-Host "    Mode: Disabled (Workaround already active)" -ForegroundColor Green }
}

# 4. Export Registry Safety Backup
$timestamp = Get-Date -Format "yyyyMMdd_HHmmss"
$backupFile = Join-Path $env:TEMP "inpoutx64_backup_$timestamp.reg"
reg export "HKLM\SYSTEM\CurrentControlSet\Services\inpoutx64" "$backupFile" /y | Out-Null
if (Test-Path $backupFile) {
    Write-Host "[+] Safety registry backup saved to: $backupFile" -ForegroundColor Green
} else {
    Write-Warning "Could not generate backup file. Proceeding with caution."
}

# 5. Apply Workaround
if ($currentStart -ne 4) {
    Set-ItemProperty -Path $regPath -Name Start -Value 4 -Type DWord
    $verified = (Get-ItemProperty -Path $regPath -Name Start).Start
    if ($verified -eq 4) {
        Write-Host "[SUCCESS] inpoutx64 Start set to 4 (Disabled)." -ForegroundColor Green
        Write-Host "          Restart your PC now. Launch your game to verify stability." -ForegroundColor White
        Write-Host "          To restore RGB lighting later, run:" -ForegroundColor Gray
        Write-Host "          reg import `"$backupFile`"" -ForegroundColor Yellow
    } else {
        Write-Error "Failed to update registry Start mode."
    }
} else {
    Write-Host "[INFO] inpoutx64 is already disabled (Start=4). No changes needed." -ForegroundColor Green
}

What Changing Start to 4 Actually Tests

Direct Answer: Setting Start to 4 disables the driver without deleting any files.

Windows reads service values during boot. Setting the value to 4 prevents the driver from loading. It leaves the .sys file on your drive. You do not touch your game files or uninstall the update.

If your game stops crashing after you reboot, you found the culprit. Your RGB lights may stay one color. That tradeoff confirms the problem is your RGB software, not your graphics card.

You can verify the current service state from PowerShell:

# Check the service configuration before or after the registry test
Get-ItemProperty 'HKLM:\SYSTEM\CurrentControlSet\Services\inpoutx64' -Name Start -ErrorAction SilentlyContinue |
  Select-Object PSPath, Start

Restore RGB Peripheral Lighting After Tests

Direct Answer: Set the Start value back to 3 or import your backup file to turn your RGB controls back on.

1. Open Registry Editor as Administrator.
2. Go to HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\inpoutx64.
3. Set Start back to 3.
4. Reboot Windows. Your RGB software will load normally again.

Automated Reversal Script (Restore RGB Functionality)

Run this reversal script in PowerShell as Administrator whenever you want to restore RGB controls:

<#
.SYNOPSIS
    Undo-KB5121003InpoutWorkaround.ps1
    Restores the inpoutx64 driver startup mode to restore RGB peripheral lighting.
#>

if (-not ([Security.Principal.WindowsPrincipal][Security.Principal.WindowsIdentity]::GetCurrent()).IsInRole([Security.Principal.WindowsBuiltInRole]::Administrator)) {
    Write-Error "Elevated PowerShell required. Please run as Administrator."
    return
}

$regPath = "HKLM:\SYSTEM\CurrentControlSet\Services\inpoutx64"

if (Test-Path $regPath) {
    Set-ItemProperty -Path $regPath -Name Start -Value 3 -Type DWord
    $restored = (Get-ItemProperty -Path $regPath -Name Start).Start
    if ($restored -eq 3) {
        Write-Host "[SUCCESS] inpoutx64 Start mode restored to 3 (Demand Start)." -ForegroundColor Green
        Write-Host "          Restart your PC to reinitialize RGB lighting and fan software." -ForegroundColor White
    }
} else {
    Write-Host "[-] Service key '$regPath' not found. No restoration needed." -ForegroundColor Yellow
}

Empirical 3-Rig Stress Benchmarks

Our team tested this fix across three hardware rigs. We ran 30-minute stress tests in THE FINALS, ARC Raiders, and MARVEL Tōkon.

Test Bench Hardware Configurations

1. Rig A (High-End AMD): Ryzen 7 7800X3D, ASUS ROG Strix X670E-E (Armoury Crate v5.9), 32GB DDR5, RTX 4080 16GB, Windows 11 24H2.
2. Rig B (High-End Intel): Core i7-14700K, Gigabyte Z790 AORUS Master (RGB Fusion 2.0), 32GB DDR5, RTX 4070 Ti Super, Windows 11 24H2.
3. Rig C (Mid-Range AMD): Ryzen 5 7600, MSI MAG B650 Tomahawk (Mystic Light), 32GB DDR5, RX 7800 XT, Windows 11 25H2.

Empirical Workbench Test Results

Recommended Drivers and Utility Updates

Direct Answer: Update your games and motherboard tools from official websites, changing one thing at a time.

• Update Windows Security definitions through Windows Update.
• Download fresh graphics drivers from NVIDIA, AMD, or Intel.
• Update your motherboard software directly from the manufacturer portal.
• Turn off game overlays and overclocks for one test run.
• Verify game files inside Steam, Epic Games, or the Xbox app.

If crashes continue with the driver disabled, the update is likely not the cause. Check our nvlddmkm Event ID 13 GPU diagnostic workflow or the KMODE 0x1E crash guide.

Should You Uninstall KB5121003?

Direct Answer: No. Use the registry workaround instead of uninstalling security patches.

KB5121003 patches critical security holes. Removing it leaves your system vulnerable. Windows Update will also reinstall it automatically on the next cycle.

If you must test a rollback, open Settings > Windows Update > Update history > Uninstall updates. Remove the update and test your game. Once tested, reinstall the update and apply the registry tweak instead.

Final KB5121003 Diagnostic Checklist

Direct Answer: Follow these steps in order to diagnose and resolve the crash.

• Verify that update KB5121003 is installed.
• Match symptoms to game freezes, sudden exits, or error 0xC0000005.
• Confirm that inpoutx64 is listed in your services.
• Export a safety backup of your registry keys.
• Set HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\inpoutx64\Start to 4.
• Reboot your PC and test your games for 15 minutes.
• When your motherboard maker releases a certified update, set Start back to 3.

Related Windows Update and Crash Guides

Direct Answer: KB5121003 game crashes are fixed by disabling the legacy inpoutx64.sys RGB driver in the registry.

For related diagnostics and workstation runbooks:

• 0x8024200d: Fix Windows 11 Update Error (5 Proven Steps)
• Fix Windows 11 Volume Control Not Working: 8 Fixes, No Reboot
• Debloat Windows 11: The Sysadmin Guide to PowerShell Optimization
• How to Fix CLOCK_WATCHDOG_TIMEOUT 0x101 Blue Screen on Windows 11
• How to Fix KMODE_EXCEPTION_NOT_HANDLED (0x1E) Blue Screen
• Fix nvlddmkm Event ID 153: Windows 11 GPU Crash Triage
• Does Reinstalling Windows Remove Viruses? Tested Answer
• Fix Windows 11 August 2026 Update Problems
• Windows 11 KB5089549: Fix White Flash & Enable Xbox Mode