KB5121003 Sparks Game Crashes After Microsoft’s Latest Update

Windows 11 KB5121003 is causing game crashes and unexpected system reboots for some users, particularly when playing ARC Raiders and The Finals. The issue appears connected to a third-party kernel driver that conflicts with changes introduced by Microsoft’s latest Windows 11 update.

Microsoft released KB5121003 as part of the August 2026 Patch Tuesday, which addressed more than 400 security issues.

However, Microsoft currently lists no known issues with KB5121003 in its official release notes.

Windows 11 KB5121003 is crashing games

Users started reporting frequent crashes shortly after installing the August update.

Affected players have encountered several issues, including GameThread hang errors, EXCEPTION_ACCESS_VIOLATION messages, sudden game crashes, and unexpected Windows reboots.

The problems have affected ARC Raiders players, while Embark, the developer behind ARC Raiders and The Finals, has acknowledged the issue.

According to Windows Latest, Embark has linked the crashes to KB5121003.

inpoutx64.sys appears to trigger the crashes

Embark says the problem involves inpoutx64.sys, a third-party kernel-level port access driver that some hardware utilities and other applications use.

KB5121003 appears to introduce a compatibility problem with the driver, although the specific Windows change responsible for the crashes remains unclear.

One affected user discovered that a Razer Update Tool had installed inpoutx64.sys on their PC, suggesting some users may have the driver without realizing it.

The driver itself appears to be the important factor rather than ARC Raiders alone, which could explain why the Windows update causes instability on only some systems.

Embark recommends removing the affected driver

Embark recommends stopping and removing inpoutx64.sys from affected systems.

Some players report that disabling the related service and restarting Windows also prevents the crashes without requiring them to remove the driver completely.

Others say uninstalling KB5121003 resolves the crashes and unexpected reboots. However, removing a security update also removes the fixes Microsoft included in the August Patch Tuesday release.

Embark says it is working on a long-term fix for the compatibility issue.

For now, users experiencing crashes after installing KB5121003 may want to check whether inpoutx64.sys exists on their systems and whether a hardware utility installed it.