Windows 11 KB5121003 is August 2026’s big security update that fixes over 400 security issues, but it’s causing major issues for some games. Gamers told Windows Latest that ARC Raiders and The Finals are among the games that crash after installing the mandatory update, and the game studio behind both titles says the Windows Update is responsible.
“We’re aware of a new crash introduced with the release of a Windows update (KB5121003) that may be affecting some of you,” Embark, the studio behind ARC Raiders, wrote in a message on Discord. “The team is working on a fix, and we will keep you posted on any updates.”
KB5121003 is a mandatory Windows Update released on August 11, and it advances PCs to Build 26200.9168 if you’re on version 25H2, and 26100.9168 for those on 24H2. If you’re not sure what build you’re running, you can open Settings > System > About and find the OS build number.
We’ve been testing the August 2026 Update across our machines, and we’ve not spotted any major problems so far. In the official release notes, Microsoft also says it is not aware of any issues with the update.
However, user reports tell us a different story, and Embark’s statement also confirms that there’s something wrong with Windows 11 KB5121003, at least on some PCs.
Windows 11 KB5121003 is crashing games on some PCs
Shortly after the August 2026 Update rolled out, we started getting messages from gamers, particularly those who play ARC Raiders, saying their game suddenly started crashing.
At first, I wondered if it was due to a recent driver update, as we’ve had similar reports in the past where Nvidia or AMD caused issues and the blame shifted to Microsoft. But this time, it looks like Windows 11 KB5121003 made a change that broke compatibility with a driver called inpoutx64.sys.
As some users noted on Reddit, ARC Raiders started crashing after the update was installed, and there are also reports of system reboots when it happens. One gamer reported six crashes, with some of them immediately rebooting Windows.
Windows Latest previously confirmed that the August 2026 Update itself can cause multiple reboots during installation due to the Secure Boot certificate rollout, but that’s different. Those reboots happen while the update is being installed, not while you’re playing a game.
If you’re affected, you may see different errors, but reports we’ve seen include “Hang detected on GameThread” and EXCEPTION_ACCESS_VIOLATION after Windows 11 KB5121003 was installed.
Until now, it was unclear what broke games such as ARC Raiders, which worked alright until a few days ago, but Embark has now shed some light on the problem.
Windows 11 KB5121003 appears to have broken compatibility with inpoutx64.sys
It turns out that Windows 11 KB5121003 appears to have made a change that affected compatibility with inpoutx64.sys, which is a third-party kernel-level port access driver used by some hardware utilities and other apps.
“This is a crash related to the file inpoutx64.sys, which changed with the Windows update,” Embark noted in a Discord post. “We’re working towards a long-term fix but in the meantime there is a work-around solution that will safely remove the file in question and allow you to play the game without issue.”
Embark also shared the following workaround for affected users:
- Open the Start menu in Windows and type ‘cmd’ to find the Command Prompt.
- Right-click on the Command Prompt and select ‘Run as Administrator.’
- In the Command Prompt window, type ‘sc stop inpoutx64’.
- Press Enter.
- Then type ‘sc delete inpoutx64’ and press Enter. Close the window.
- Open File Explorer and navigate to C:WindowsSystem32drivers.
- Locate the file inpoutx64.sys and delete the file.
Embark’s finding aligns with what we’re hearing from gamers. For example, one ARC Raiders user who investigated their own crashes found that inpoutx64.sys had been installed by a Razer Update Tool.
That user found that simply disabling the inpoutx64 service and restarting the PC was enough to stop the crashes on their machine. However, Embark’s official workaround goes further by stopping and deleting the service and removing inpoutx64.sys.
Right now, we don’t know exactly what Windows 11 KB5121003 changed that broke compatibility with inpoutx64.sys, but we’ll likely hear back from Microsoft soon.
Several affected users also say removing Windows 11 KB5121003 resolves the issue, which further points to a compatibility problem between the update and the driver. Windows Latest has also seen reports of some anti-cheat-related software crashing after the update, with affected users reporting similar results after uninstalling KB5121003.
We’re also seeing similar crash reports involving other games, including Marvel Tōkon: Fighting Souls.
Separately, there are early reports of display refresh rates unexpectedly dropping, black screens, broken HDR behaviour, and other graphics-related problems after the August 2026 cumulative update.
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