Windows 11 KB5121003 Update Causes Game Crashes and System Issues

Microsoft's August 2026 Patch Tuesday update, designated KB5121003, has been causing serious issues on some PCs since its release on August 11, 2026. The mandatory security patch, which addresses over 400 vulnerabilities including an actively exploited zero-day tracked as LegacyHive, has inadvertently introduced compatibility problems affecting gamers and general users alike.

Game Crashes: ARC Raiders and The Finals

The gaming community has been particularly affected by KB5121003. Multiple outlets including PCWorld, Windows Latest, and Notebookcheck have reported a surge in game crashes since the update's installation. Titles such as ARC Raiders and The Finals, both developed by Swedish studio Embark Games, have been especially impacted.

Embark Games acknowledged the issue in a Discord post, stating: We are aware of a new crash introduced with the release of a Windows update (KB5121003) that may be affecting some of you. The team is working on a fix, and we will keep you posted on any updates.

The root cause has been traced to a third-party kernel-level driver called inpoutx64.sys, which conflicts with changes introduced by KB5121003. This driver is used by some hardware utilities and other applications. In some cases, the driver was installed by tools such as Razer's update utility. The incompatibility causes crashes with error messages including Hang detected on GameThread and EXCEPTION_ACCESS_VIOLATION.

Similar crash reports have surfaced for other games including Marvel Tokon: Fighting Souls and some anti-cheat software. Removing KB5121003 entirely has also resolved the issue for affected users, though this is not recommended due to the security vulnerabilities the patch addresses.

Embark Games Workaround

Embark Games has provided a temporary workaround for affected users. The steps involve disabling and removing the problematic driver through Command Prompt:

1. Open the Start menu in Windows and type cmd to find the Command Prompt.
2. Right-click on the Command Prompt and select Run as Administrator.
3. In the Command Prompt window, type sc stop inpoutx64 and press Enter.
4. Then type sc delete inpoutx64 and press Enter.
5. Close the Command Prompt window.
6. Open File Explorer and navigate to C:\Windows\System32\drivers\.
7. Locate the file inpoutx64.sys and delete it.

Some affected users found that simply disabling the inpoutx64 service and restarting the PC was sufficient to stop the crashes. However, Embark's official workaround removes the service and driver file entirely for a more permanent temporary solution.

Windows Hello and Display Issues

Beyond gaming, KB5121003 has caused other system problems. Windows Latest reported isolated cases of Windows Hello PIN sign-in failures after the update. In one case, the PIN credential key becomes corrupted upon every reboot, forcing users to re-enroll their PIN each time they sign in. One user described the issue as an infinite loop where Windows deletes and recreates the key each reboot, but the new key becomes corrupted again by the next boot.

Display-related problems have also been reported, including unexpected drops in refresh rates, black screens, and broken HDR behavior. These issues appear linked to display-related changes bundled into the update.

Microsoft's Response

Microsoft has not yet publicly acknowledged the game crash issues in its official release notes, which state: Microsoft is not currently aware of any issues with this update. However, Neowin reported on August 20, 2026, that Microsoft is investigating whether KB5121003 breaks games. The company typically urges users who experience issues to report them through the Feedback Hub.

Microsoft has warned against delaying the installation of security updates, recommending deployment within three days due to rising AI-powered threats. The August 2026 update patches at least 37 remote code execution bugs and five elevation-of-privilege bugs, along with the actively exploited LegacyHive zero-day vulnerability.

Additional Update Features

Despite the reported issues, KB5121003 includes several new features and improvements:

• Windows Hello Enhanced Sign-in Security (ESS) support for external fingerprint sensors
• Ability to uninstall AI models from Copilot+ PCs
• Touchpad gesture customization for scroll and zoom speed
• Voice Isolation for Voice Access to filter background noise
• Fluid Dictation for Voice Typing with integrated tooltips
• File Explorer improvements including better file size units and middle-click tab opening
• Windows Search typo handling and two-character query support
• Power settings automatically applied to all power plans
• More accurate Windows Update progress estimates

User Options and Recommendations

Affected users have several options to address the issues caused by KB5121003:

For game crashes: The safest immediate solution is to follow Embark Games' workaround and remove the inpoutx64.sys driver. Users should first identify which software installed the driver to prevent reinstallation.

For other issues: Users can uninstall KB5121003 through Settings, Windows Update, Update History, and Uninstall Updates. However, this is only recommended if the PC is severely affected, as removing the update exposes the system to over 400 unpatched security vulnerabilities including the actively exploited LegacyHive zero-day.

General recommendation: Unless the PC is unusable, users should ideally wait for an official fix from Microsoft or the September 2026 update. The security risks of running an unpatched system outweigh the inconvenience of temporary workarounds for most users.

Conclusion

The Windows 11 KB5121003 update represents a significant security release that has inadvertently introduced compatibility issues for a subset of users, particularly gamers. While the inpoutx64.sys driver conflict has a documented workaround, the broader pattern of issues including Windows Hello failures and display problems suggests that the update's changes were more impactful than Microsoft's testing anticipated. Users should apply the available workarounds while awaiting official remediation from Microsoft, balancing the need for security patches against the practicality of daily system use.

Frequently Asked Questions

Q: What is the specific Windows 11 update causing issues?
A: The problematic update is KB5121003, released on August 11, 2026. It is a mandatory security update that addresses over 400 vulnerabilities, including an actively exploited zero-day known as LegacyHive.

Q: Which games are affected by KB5121003?
A: ARC Raiders and The Finals, both developed by Embark Games, have been particularly affected. Similar crashes have been reported for Marvel Tokon: Fighting Souls and some anti-cheat software. The root cause is a conflict with the third-party driver inpoutx64.sys.

Q: How can I fix game crashes caused by KB5121003?
A: Embark Games recommends running Command Prompt as Administrator, executing sc stop inpoutx64 and sc delete inpoutx64, then deleting the inpoutx64.sys file from C:\Windows\System32\drivers\. Alternatively, uninstalling KB5121003 resolves the issue but exposes your system to security vulnerabilities.

Q: Is Microsoft aware of the issues?
A: As of August 20, 2026, Microsoft's official release notes state they are not currently aware of any issues with the update. However, Neowin reported that Microsoft is investigating the game crash reports. Users are urged to report issues through the Feedback Hub.