- Status: Investigating / Confirmed by third-party developers
- Affected Versions: Windows 11 25H2 (Build 26200.9168) and 24H2 (Build 26100.9168)
- KB Article: KB5121003
- Release Date: August 11, 2026
Microsoft rolled out KB5121003 as the mandatory August 2026 Patch Tuesday security update, advancing systems to Build 26200.9168 for version 25H2 and Build 26100.9168 for version 24H2. While the update addresses over 400 security vulnerabilities, a growing number of users are reporting stability problems that contradict Microsoft’s official release notes, which state the company is not aware of any issues.
The most prominent complaints involve sudden game crashes and display regressions. Developers behind affected titles have confirmed the Windows update is the culprit, pointing to a specific compatibility break with a widely used kernel-level driver.
Windows 11 KB5121003 and the inpoutx64.sys Conflict
Reports of instability surfaced shortly after the update began deploying. Gamers playing ARC Raiders and The Finals noticed their sessions terminating unexpectedly, often accompanied by system reboots. Embark Studios, the developer behind ARC Raiders, acknowledged the problem in a Discord announcement, confirming that a new crash was introduced by the patch.
Investigation by affected users and the developer revealed the root cause: a change in KB5121003 that broke compatibility with inpoutx64.sys. This is a third-party kernel-mode driver used for direct port I/O access, commonly installed by hardware utility suites like the Razer Update Tool and various peripherals. When the game attempts to communicate through this driver, the updated Windows kernel triggers a fatal exception.
Users experiencing the crash typically see error messages such as “Hang detected on GameThread” or EXCEPTION_ACCESS_VIOLATION before the application closes. In severe cases, the crash forces an immediate system restart, adding frustration to an already disruptive experience. It is worth noting that these reboots are distinct from the multiple restarts some users experienced during the initial installation phase, which Microsoft attributed to Secure Boot certificate rollouts.
Official Workaround for Affected Users
Until Embark releases a long-term patch that bypasses the driver dependency, the studio has published a manual workaround to restore stability. The process involves disabling the conflicting service and removing the driver file from the system directory.
- Press the Start key, type
cmd, right-click Command Prompt, and select Run as administrator. - Type
sc stop inpoutx64and press Enter. - Type
sc delete inpoutx64and press Enter. Close the Command Prompt window. - Open File Explorer and navigate to
C:\Windows\System32\drivers\. - Locate
inpoutx64.sysand delete the file.
Some users have reported that simply stopping the service and restarting the PC is sufficient to prevent crashes, but removing the file ensures the driver cannot reload automatically. If you rely on the hardware features that require this driver, you may need to wait for a patched version of the utility or a future Windows update that restores compatibility.
Other Reported Issues
Beyond game crashes, Windows Latest has compiled reports of additional stability and visual regressions following the installation of KB5121003. Several users on Reddit and Microsoft’s feedback hub have documented unexpected drops in display refresh rates, even after manually locking the setting in Windows Display settings. Others are experiencing black screens upon waking from sleep mode or persistent HDR behavior that fails to engage correctly, resulting in washed-out colors and reduced contrast.
Anti-cheat software has also come under scrutiny. Multiple users report that anti-cheat services crash or fail to initialize after the update, which can prevent access to online multiplayer titles. Uninstalling KB5121003 has been cited as a temporary resolution for these specific cases, further pointing to a kernel-level conflict introduced by the patch.
What This Means for You
If you are currently running version 24H2 or 25H2 and have not yet installed the August update, you may want to pause and monitor user feedback for a few days before proceeding. While security patches are critical, this situation highlights a recurring tension between rapid deployment cycles and third-party driver compatibility. Microsoft’s decision to make this update mandatory means devices will eventually receive it automatically, so understanding the potential impact is essential for gamers and power users.
For those already affected, the workaround provided by Embark is safe to implement and reversible if you later need to reinstall the driver. Keep in mind that future updates to your hardware utilities may reintroduce inpoutx64.sys, at which point you might need to repeat the process or wait for a coordinated fix between the driver developer and Microsoft.
How to Check Your Build
To verify whether your system has received the August 2026 update, open Settings and navigate to System > About. Under Windows specifications, check the Version and OS build numbers. If your build matches 26200.9168 or 26100.9168, you are running the patched version. If you encounter the crashes described above, applying the workaround or pausing updates until a resolution is issued is your best course of action.
Source: Windows Latest
Over to you: Have you experienced game crashes or display issues after installing KB5121003, and did the workaround resolve the problem?
