Some PC games have stopped working properly on machines that installed KB5121003, the August cumulative update for Windows 11. Microsoft has acknowledged the problem as a known issue and pointed to drivers that ship with RGB lighting features as the trigger. There is a certain irony here: the flashier the gaming rig, the more likely it is to be affected.

Windows 11 24H2 and 25H2 are affected

KB5121003 shipped on August 11, 2026 and targets Windows 11 versions 24H2 and 25H2, which correspond to OS builds 26100.9168 and 26200.9168. It arrived as part of the monthly security release, so if automatic updates are enabled, it is safe to assume the package is already installed.

Microsoft later added the game failures to the known issues published for this update. In practice, user reports came first and the official acknowledgement followed.

The crash is not always limited to the game

The reported symptoms cluster around game launch. Applications stop responding, exit without warning, display an EXCEPTION_ACCESS_VIOLATION error, or the device restarts with no warning at all. That last one goes beyond a crashed game, since anything else running at the time goes down with it.

Microsoft names three titles: ARC Raiders, MARVEL Tōkon: Fighting Souls and THE FINALS. Those are simply the games that were reported, and there is no confirmation that the impact stops there.

Drivers installed by RGB control software

According to Microsoft, the cause lies in drivers installed by peripherals or internal components that support RGB lighting, specifically components with file names similar to inpoutx64. Drivers of this type provide software with direct access to hardware I/O ports, and they are sometimes bundled with the utilities that control lighting on motherboards, memory modules, fans and keyboards.

The awkward part is that Microsoft has not named a specific vendor or product. On a custom build or a gaming desktop, it is common for the case, memory, CPU cooler and keyboard to come from different brands, each with its own lighting software. From the user side, working out which utility installed the offending driver is not straightforward.

The workaround is a registry edit, and the cost is going dark

Microsoft's suggested workaround is to edit the registry and temporarily disable the driver in question. Doing so may stop RGB lighting from working on connected peripherals, and it may also cause problems in the lighting control software itself. Restoring the feature requires putting the registry values back, so backing up the relevant keys and values before making changes is recommended.

In short, the trade is that you give up the lighting and the games run. For anyone who plays competitive titles daily that may be an easy call, but it is a workaround that people who are uncomfortable editing the registry will hesitate to attempt.

A permanent fix is still pending

There is no permanent fix yet, and no specific product or software package has been identified as the culprit. Microsoft is asking affected users to report the behavior through the Feedback Hub.

Because this is a cumulative update that includes security fixes, uninstalling it to see what happens is hard to recommend as the safe option. For now, the sensible path is to check whether the symptoms appear, apply the workaround if necessary, and wait for word of a fix.

Summary

Games are failing to launch and PCs are restarting unexpectedly on systems that installed KB5121003, the August cumulative update for Windows 11. Microsoft has acknowledged the issue and identified RGB lighting drivers as the trigger. The workaround is to disable the driver through the registry, which means losing lighting functionality in the meantime. With no permanent fix available yet, anyone running an affected configuration should keep an eye on how their system behaves after the update.

*The image is for illustrative purposes only.