Windows 11’s August cumulative update, KB5121003, released on August 11, 2026, is causing unexpected crashes and launch failures in several popular games. At least one affected studio has already confirmed the issue, and the cause comes down to how Windows now protects system memory at a low level.

What’s happening

KB5121003 strengthens HVCI (Hypervisor-protected Code Integrity), the Windows 11 feature that isolates and protects kernel memory using virtualization. That change conflicts with inpoutx64.sys, an older driver several games still rely on for low-level functions such as communicating with certain peripherals. Since the new HVCI rules flag the driver as potentially unsafe, Windows blocks it from loading, and the game either crashes or fails to launch at all.

Which games are affected

Confirmed so far:

  • ARC Raiders
  • MARVEL Tōkon: Fighting Souls
  • The Finals

The list will likely grow over the next few days as more players update and other studios using the same driver confirm the issue.

How to fix it

Embark Studios, developer of ARC Raiders and The Finals, has already published a workaround: stop and delete the Windows service tied to inpoutx64, then remove the driver file from the system. From an elevated PowerShell window:

sc stop inpoutx64
sc delete inpoutx64

Then locate and manually delete the inpoutx64.sys file, usually found in the System32/drivers folder (full path: C:/Windows/System32/drivers).

You can also fully uninstall KB5121003 from Windows Update history, which removes the conflict at the root. This isn’t recommended, though: the same update patches an actively exploited zero-day known as “LegacyHive”, so uninstalling it re-exposes your PC to that security flaw while the game issue gets sorted out.

Microsoft hasn’t commented on the inpoutx64.sys conflict yet. The most likely fix is a future cumulative update that adjusts the HVCI rules instead of relying on every studio to ship its own patch.