Windows 11 KB5121003: Game Crashes, Black Screens, and How to Fix Them

Microsoft’s August 2026 security update for Windows 11, KB5121003, closes roughly 400 security holes — including a zero-day called “LegacyHive” that lets attackers grab admin privileges. It’s also breaking things for a chunk of PC gamers. If your games started crashing, your display looks wrong, or you’re stuck re-entering your Windows Hello PIN after every reboot, here’s what’s actually going on and what to do about it.

What KB5121003 Actually Does

Released August 11, 2026, KB5121003 is a mandatory Patch Tuesday update. It moves Windows 11 25H2 to build 26200.9168 and 24H2 to build 26100.9168. You can check which build you’re on under Settings > System > About. Microsoft’s official release notes don’t list any known issues, but that doesn’t match what’s actually happening on a meaningful number of PCs.

Games Crashing After the Update

Players of ARC Raiders and The Finals started reporting crashes almost immediately after installing KB5121003 — sometimes with a full system reboot mid-crash. Embark Studios, the developer behind both games, confirmed on Discord that the crash is tied to a file called inpoutx64.sys, which “changed with the Windows update.” Similar crash reports have surfaced for Marvel Tōkon: Fighting Souls and some anti-cheat software. Typical errors include “Hang detected on GameThread” and EXCEPTION_ACCESS_VIOLATION.

inpoutx64.sys isn’t part of Windows itself — it’s a third-party kernel-level driver for low-level hardware port access, commonly installed by RGB lighting or peripheral utilities (Razer’s update tool is one confirmed source). KB5121003 changed something that broke compatibility with it, and Microsoft hasn’t explained exactly what yet.

The Workaround for Game Crashes

Embark published a temporary fix that removes the conflicting driver without touching the security update itself:

1. Open the Start menu, type cmd, right-click Command Prompt and choose Run as Administrator.
2. Type sc stop inpoutx64 and press Enter.
3. Type sc delete inpoutx64 and press Enter, then close the window.
4. Open File Explorer, go to C:\Windows\System32\drivers\, and delete inpoutx64.sys if it’s still there.

Some users have found that simply stopping the service (without deleting the file) is enough, but removing it fully matches what Embark recommends. If the utility that installed the driver runs again later, it may reinstall it, so you may need to repeat this after updating that software.

Other Problems: Black Screens, HDR, and Windows Hello

The crash issue isn’t the only complaint. Some users are reporting display refresh rates dropping unexpectedly, black screens, and broken HDR behavior after installing KB5121003. Separately, a smaller number of people are seeing Windows Hello PIN sign-in fail on every reboot — Windows deletes and recreates the PIN’s security key each time, and the new key gets corrupted again before the next boot, forcing a re-enrollment loop. There’s no confirmed fix for either of these yet beyond removing the update.

Worth knowing: KB5121003 can also trigger multiple reboots during installation because of a Secure Boot certificate rollout bundled into this update. That’s a separate, expected behavior — not a sign something’s broken, and not related to the crash or display issues above.

Should You Uninstall the Update?

Removing KB5121003 does resolve these problems for the people who’ve tried it, and you can do it from Settings > Windows Update > Update history > Uninstall updates. But it also removes patches for around 400 security vulnerabilities, including the LegacyHive zero-day, which is already being exploited in the wild. Uninstall it only if the problems genuinely make your PC unusable — for the inpoutx64.sys crash specifically, the driver removal above should fix it without giving up any security coverage. If you’re dealing with the display or Windows Hello issues instead, weigh the tradeoff carefully and check for a follow-up patch before falling back to a full uninstall.

What to Expect Next

Microsoft hasn’t issued an official acknowledgment of these problems as of this writing, which is common in the days right after a Patch Tuesday release, before enough reports accumulate. A real fix is more likely to land as an out-of-band patch or in the next monthly update than as anything you can trigger yourself beyond the driver workaround above. If you’re also seeing unrelated crash codes like KMODE_EXCEPTION_NOT_HANDLED, that’s a distinct driver conflict worth checking separately — Windows update-related driver breakage tends to show up in more than one place at once.

FAQ