Windows 11 KB5121003: Issues and Impacts

The Windows 11 KB5121003 update, released in August 2026, is a major security patch that addresses over 400 security vulnerabilities. However, despite its significance, the update has caused significant issues for certain games, including ARC Raiders and The Finals, which have been reported to crash after the update. According to game developer Embark Studios, the update is the root cause of these problems.

Game Crashes Reported After KB5121003 Update

Embark Studios acknowledged the issue in an official statement on Discord, as first reported by Windows Latest: “We’re 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.”

KB5121003, a mandatory update released on August 11, 2026, updates PCs to Build 26200.9168 for version 25H2 and Build 26100.9168 for version 24H2. Users can check their OS build number by navigating to Settings > System > About.

Issues Confirmed by User Reports

While MS’s official release notes claim no known issues, user reports tell a different story. Many gamers have reported crashes, particularly with ARC Raiders, immediately after installing the update. These crashes have been linked to a compatibility issue with a driver called inpoutx64.sys.

Inpoutx64.sys Compatibility Problems

The KB5121003 update seems to have impacted the functionality of inpoutx64.sys, a third-party kernel-level port access driver used by hardware utilities and other applications. Embark Studios confirmed this in a Discord post, stating, “This is a crash related to the file inpoutx64.sys, which changed with the Windows update. We’re working toward a long-term fix, but in the meantime, there is a workaround solution that will safely remove the file in question and allow you to play the game without issue.”

Proposed Workarounds

• Disable the inpoutx64 service and restart your PC. This may resolve the crashes for some users.
• Embark Studios has suggested an official workaround that involves stopping and deleting the inpoutx64 service and removing the driver file from the system.

Some users have discovered that the driver was installed by third-party software, such as a Razer Update Tool. Removing the associated software or disabling the service has resolved the issue for these users.

Additionally, several users have reported that uninstalling the KB5121003 update entirely eliminates the issue, further confirming the incompatibility between the update and inpoutx64.sys.

Other Problems Linked to KB5121003

Beyond game crashes, the August 2026 update has introduced other issues for some users:

• Display-related problems: Reports include unexpected drops in refresh rates, black screens, and broken HDR behavior.
• Windows Hello malfunctions: Some users have encountered PIN credential errors, requiring re-enrollment after every reboot. In one case, Windows continuously recreates a corrupted key, resulting in an infinite loop.

What to Do If You’re Affected

If you’re experiencing issues after installing KB5121003, consider the following steps:

1. Identify and disable the inpoutx64.sys driver or locate the software that installed it.
2. If the problems persist and are severe, you can uninstall the update by navigating to Settings > Windows Update > Update History > Uninstall Updates.

However, uninstalling the update should be a last resort, as the August 2026 patch addresses critical vulnerabilities, including a zero-day exploit called LegacyHive, which could grant attackers administrative privileges. MS advises users not to delay updates for more than three days due to the increasing risk of AI-powered threats.

Conclusion

While the Windows 11 KB5121003 update brings essential security fixes, its unintended consequences have caused disruptions for gamers and other users. Those affected are advised to explore workarounds or await official fixes from MS. Unless your PC becomes unusable, it is recommended to avoid uninstalling the update to maintain protection against critical security threats.

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