Microsoft released KB5121003 on August 11, 2026, as a security update for Windows 11 versions 24H2 and 25H2. The update includes security improvements and other changes, but Microsoft has confirmed a known issue affecting some games.
If games started crashing, freezing, closing unexpectedly, or restarting your PC after installing KB5121003, the update may be related.
Microsoft says the problem appears to involve certain RGB lighting peripherals or internal components that install drivers or software components with names similar to inpoutx64. Reported affected games include ARC Raiders, MARVEL Tōkon: Fighting Souls, and THE FINALS.
This guide explains what KB5121003 does, what problems have been reported, and what you can do if your Windows 11 PC is affected.
Important: KB5121003 is a security update. Do not uninstall it simply because you have heard about the problem. First, confirm that your symptoms match the known issue and try safer troubleshooting steps.
Table of Contents
- What Is Windows 11 KB5121003?
- Which Windows 11 Versions Are Affected?
- What Problems Does KB5121003 Cause?
- Why Are Games Crashing After KB5121003?
- How to Check If KB5121003 Is Installed
- Fix 1: Restart Your PC
- Fix 2: Update Your RGB and Peripheral Software
- Fix 3: Temporarily Disable RGB Control Software
- Fix 4: Update Your Game
- Fix 5: Update Windows and Check for a New Fix
- Fix 6: Repair the Affected Game
- Fix 7: Uninstall KB5121003
- Fix 8: Uninstall the Update From Windows RE
- Fix 9: Repair Windows System Files
- Fix 10: Report the Problem to Microsoft
- Should You Uninstall KB5121003?
- Frequently Asked Questions
- Related Articles
- Final Thoughts
What Is Windows 11 KB5121003?
KB5121003 is the August 11, 2026 security update for Windows 11 24H2 and 25H2.
The update includes security improvements and quality changes. It also includes additional Secure Boot certificate deployment coverage and other improvements.
The update was released through Windows Update and Microsoft Update. It is also available through the Microsoft Update Catalog.
The problem is not that KB5121003 breaks every Windows 11 PC.
Microsoft has confirmed a specific known issue involving certain games and RGB-related drivers or software.
Which Windows 11 Versions Are Affected?
What Does Windows 11 24H2 Mean?
24H2 means:
- 24 = 2024
- H2 = second half of the year
Windows 11 24H2 is the Windows 11 feature version released in the second half of 2024. It uses the 26100 build family.
What Does Windows 11 25H2 Mean?
25H2 means:
- 25 = 2025
- H2 = second half of the year
Windows 11 25H2 is the newer Windows 11 feature version. It uses the 26200 build family.
These are Windows versions, not different editions. For example, you can have Windows 11 Home 24H2 or Windows 11 Pro 24H2. The same applies to 25H2.
Are 24H2 and 25H2 Completely Different Windows Versions?
Not exactly.
Windows 11 25H2 builds on the technology and updates delivered through 24H2. For compatible PCs upgrading from 24H2, Microsoft uses an enablement package, making the upgrade relatively small compared with a completely new Windows installation.
In simple terms, 25H2 is the newer feature version, while 24H2 is its predecessor.
What About Windows 11 26H1?
Windows 11 26H1 is different. It does not receive KB5121003.
Windows 11 26H1 has its own August 2026 security update, KB5121000.
Therefore, if you are troubleshooting KB5121003, first check whether your PC is running 24H2 or 25H2.
How to Check Your Windows 11 Version
The easiest way is to use the winver command:
- Press Windows + R.
- Type
winver. - Press Enter.
- Look for Version in the About Windows window.
You may see something like:
Version 24H2 (OS Build 26100.xxxx)
or:
Version 25H2 (OS Build 26200.xxxx)
If you see 24H2 or 25H2, KB5121003 is the relevant August 2026 update for your Windows version.
Windows 11 24H2 vs 25H2
| Windows Version | Meaning | Build Family | KB5121003 |
|---|---|---|---|
| 24H2 | 2024, second half | 26100 | Yes |
| 25H2 | 2025, second half | 26200 | Yes |
| 26H1 | 2026, first half | 28000 | No — uses KB5121000 |
Important: The Windows version and Windows edition are different things. 24H2/25H2 describe the Windows release version, while Home/Pro/Enterprise describe the edition.
What Problems Does KB5121003 Cause?
Microsoft's current known-issue information specifically mentions certain games becoming unresponsive after KB5121003.
Reported symptoms include:
- A game freezes.
- A game stops responding.
- A game closes without warning.
- Windows displays an
EXCEPTION_ACCESS_VIOLATIONerror. - The PC restarts unexpectedly.
The affected games identified by Microsoft are:
- ARC Raiders
- MARVEL Tōkon: Fighting Souls
- THE FINALS
Microsoft says the problem may be associated with RGB-related peripherals or internal components that install drivers or software components with filenames similar to inpoutx64.
Other reports have described additional problems after the update, including display problems and Windows Hello PIN issues. However, these should not automatically be attributed to KB5121003 without checking the individual PC configuration and Microsoft's latest release-health information.
If the update appears to have caused other Windows problems rather than game crashes, see our guide on fixing Windows 11 Wi-Fi problems.
If you are experiencing screen flickering rather than game crashes, see our guide on fixing screen flickering in Windows 10 and Windows 11.
Why Are Games Crashing After KB5121003?
The problem appears to involve a conflict between the Windows update and certain third-party RGB or hardware-control components.
One important component being investigated is associated with the inpoutx64 driver.
These drivers can be installed by software used to control RGB lighting or other hardware functions.
Microsoft has not said that every system containing such software will experience the problem. Its current investigation specifically concerns systems where these components interact with affected games.
This means your graphics card may not be the problem.
Before replacing hardware or reinstalling Windows, check the software and drivers installed on your PC.
If you are also seeing high GPU usage or desktop display problems, our guide to Desktop Window Manager high GPU usage may help.
How to Check If KB5121003 Is Installed
Method 1: Windows Settings
- Press Windows + I.
- Select Windows Update.
- Select Update history.
- Look under Quality Updates.
- Search for KB5121003.
If it is listed, the August 2026 update is installed.
You can also check your OS build by pressing Windows + R, entering winver, and pressing Enter.
Fix 1: Restart Your PC
A restart should be your first step.
If Windows has just installed KB5121003, background processes and drivers may not have fully restarted.
- Save your work.
- Close your applications.
- Select Start > Power > Restart.
- Wait for Windows to start completely.
- Test the affected game again.
If the game continues to crash, move to the next fix.
Fix 2: Update Your RGB and Peripheral Software
Check the software used to control:
- RGB keyboards
- RGB mice
- RGB headsets
- RGB fans
- Motherboard lighting
- Gaming controllers
- Internal lighting controllers
Open the manufacturer's software and check for updates.
Also check the manufacturer's support website for a newer Windows 11-compatible version.
This is particularly important because Microsoft says the known issue involves certain RGB-related components and drivers.
Fix 3: Temporarily Disable RGB Control Software
If your game crashes immediately after launching, temporarily disable RGB control software.
The exact procedure depends on the software.
As a test:
- Close the RGB application.
- Open Task Manager with Ctrl + Shift + Esc.
- Look for related RGB or hardware-control processes.
- End the relevant application if necessary.
- Start the game again.
If the game works normally afterward, the RGB software or one of its drivers may be involved.
Do not permanently remove a driver unless you know exactly what it belongs to.
Fix 4: Update Your Game
Game developers may release compatibility fixes after Microsoft identifies an operating-system problem.
Open the game launcher you use and check for updates.
For example:
- Steam
- Epic Games Launcher
- Xbox app
- Microsoft Store
- The game's own launcher
Restart the PC after installing a game update and test again.
Fix 5: Update Windows and Check for a New Fix
Microsoft is investigating the KB5121003 game issue.
Therefore, check Windows Update regularly for a newer cumulative update or a revised fix.
- Press Windows + I.
- Select Windows Update.
- Select Check for updates.
- Install available updates.
- Restart your PC.
If Windows Update itself is behaving strangely or your PC has become unstable, our guide to fixing corrupted files in Windows 11 and Windows 10 can help you check and repair damaged system components.
Fix 6: Repair the Affected Game
If only one game is affected, repair or verify its installation before removing a Windows security update.
Depending on the launcher, look for an option such as:
- Verify integrity of game files
- Repair
- Verify files
- Scan and repair
After the process finishes, restart the game.
If several different games began crashing immediately after KB5121003, however, the Windows update or a shared driver becomes more likely.
Fix 7: Uninstall KB5121003
If your PC became unstable immediately after installing KB5121003 and the problem continues, you can consider uninstalling the update.
Uninstall KB5121003 From Settings
- Press Windows + I.
- Select Windows Update.
- Select Update history.
- Select Uninstall updates.
- Find KB5121003.
- Select Uninstall.
- Restart the PC.
Not every Windows update can be removed, so the uninstall option may not be available on every system.
Important
Removing KB5121003 also removes the security improvements included in that update.
If uninstalling it fixes your problem, keep checking Windows Update for a newer Microsoft fix rather than leaving the security update removed indefinitely.
Fix 8: Uninstall the Update From Windows RE
If Windows will not start normally, you may be able to remove the latest quality update from Windows Recovery Environment.
If Windows will not start normally, you may also need to use Windows 10 and 11 Safe Mode to troubleshoot drivers and third-party software before removing an update.
Enter Windows RE
If you can still access Windows:
- Open Settings.
- Select System > Recovery.
- Under Advanced startup, select Restart now.
You can also hold Shift while selecting Restart from the Power menu.
Windows RE provides recovery tools, including the option to uninstall recent updates.
Remove the Latest Quality Update
Select:
Troubleshoot > Advanced options > Uninstall Updates
Then choose the option to uninstall the latest quality update.
Microsoft specifically lists uninstalling a recent update as a recovery option when a PC develops problems after an update.
Fix 9: Repair Windows System Files
If Windows itself has become unstable, check the system files.
Open Command Prompt as administrator and run:
DISM.exe /Online /Cleanup-image /Restorehealth
Wait for the process to finish.
Then run:
sfc /scannow
Restart your computer when the scan finishes.
If your PC has become noticeably slower or unstable after the update, see our guide on how to fix a slow Windows 11 PC for additional troubleshooting steps.
Fix 10: Report the Problem to Microsoft
If your PC is affected by the KB5121003 game problem, report it to Microsoft.
Press:
Windows + F
This opens Feedback Hub.
Include:
- Windows version
- Windows build
- KB5121003
- Game name
- Error message
- When the problem started
- RGB or peripheral software installed
- Whether uninstalling the update changed the problem
Should You Uninstall KB5121003?
Not immediately.
KB5121003 is a security update, so removing it has a security cost.
If your PC works normally and you do not experience the reported problem, there is generally no reason to remove the update simply because other users have encountered problems.
If you are experiencing repeated game crashes or unexpected restarts after the update, try these steps first:
- Restart Windows.
- Update your games.
- Update RGB and peripheral software.
- Temporarily disable RGB software.
- Check for newer Windows updates.
- Repair the affected game.
- Only then consider uninstalling KB5121003.
Frequently Asked Questions
Is KB5121003 causing game crashes?
Microsoft has confirmed a known issue involving certain games after KB5121003. The investigation points to certain RGB-related peripherals or internal components and drivers with names similar to inpoutx64.
Which games are affected by KB5121003?
Microsoft currently identifies ARC Raiders, MARVEL Tōkon: Fighting Souls, and THE FINALS in its known-issue documentation.
Does KB5121003 affect Windows 11 24H2?
Yes. KB5121003 applies to Windows 11 version 24H2 and version 25H2.
Does KB5121003 affect Windows 11 25H2?
Yes. Microsoft lists Windows 11 25H2 among the versions receiving KB5121003.
What is the difference between Windows 11 24H2 and 25H2?
Windows 11 24H2 is the 2024 feature version, while 25H2 is the newer 2025 feature version. Both are Windows 11 versions, not editions such as Home or Pro.
Is Windows 11 25H2 better than 24H2?
25H2 is the newer Windows 11 feature version and has a longer support period. However, you should not change versions solely because of a problem with KB5121003. Check Microsoft's current compatibility and update guidance first.
How do I know whether I have Windows 11 24H2 or 25H2?
Press Windows + R, type winver, and press Enter. The About Windows window displays your Windows version and OS build.
Does KB5121003 affect Windows 11 26H1?
No. KB5121003 is for Windows 11 24H2 and 25H2. Windows 11 26H1 receives a separate August 2026 security update, KB5121000.
What is inpoutx64?
inpoutx64 refers to a third-party kernel-level driver or component used by some software that interacts directly with hardware. Microsoft says components with names similar to inpoutx64 are associated with its investigation into the KB5121003 game problem.
Should I uninstall KB5121003?
Only if you are experiencing problems that appear to be caused by the update and other troubleshooting steps have not helped. Remember that removing a security update can leave your PC without its security fixes.
Can I reinstall KB5121003 later?
Yes. If you temporarily uninstall the update, continue checking Windows Update for a newer version or Microsoft fix. Avoid leaving an important security update removed longer than necessary.
How do I know if KB5121003 is installed?
Go to Settings > Windows Update > Update history and look under Quality Updates for KB5121003.
Related Articles
If you are troubleshooting other Windows 11 problems after installing an update, these Computerdok guides may also help:
- Fix Windows 11 Wi-Fi Problems
- Fix Corrupted Files in Windows 11 & Windows 10
- How to Boot Windows 10 & 11 in Safe Mode
- How to Fix a Slow Windows 11 PC
- Fix Screen Flickering in Windows 10 & Windows 11
- Fix “Your PIN Is No Longer Available” in Windows 11 & Windows 10
- Desktop Window Manager High GPU Usage: How to Fix
Final Thoughts
Windows 11 KB5121003 is an important security update, but Microsoft is currently investigating a specific compatibility problem affecting some games.
If your game started freezing, closing, displaying EXCEPTION_ACCESS_VIOLATION, or causing the PC to restart after installing KB5121003, check your RGB lighting software and related drivers first.
Do not immediately assume that your graphics card or Windows installation is damaged.
Start with the safer fixes in this guide. If the problem remains and the timing clearly matches the update, uninstalling KB5121003 can be considered as a temporary workaround. Then monitor Windows Update for Microsoft's next fix.