Windows 11 October 2026 Update: Game Fixes & Known Issues

Microsoft's October 2026 security update for Windows 11, KB5127648, arrived on October 13. It fixes two problems that hit PC players over the last three weeks: games and apps closing because of a Dolby Digital (AC-3) audio bug, and mouse stutter in some games. It does not say anything about the launch crashes reported in Rainbow Six Siege X, Battlefield 6 and other games with anti-cheat.

Here is what happened, what is fixed, and what to do if a game still crashes on your PC.

Timeline

Date	What happened
September 22, 2026	Microsoft releases KB5124010, an optional preview update for Windows 11 24H2 and 25H2 (September 29 for 26H2).
September 25, 2026	Players report crashes in Battlefield 6, Battlefield 2042, WARDOGS and Fallout: New Vegas after the preview, according to reports on Reddit and Steam picked up by Neowin and TweakTown.
September 29, 2026	Windows 11 26H2 becomes available, through the KB5121794 enablement package.
Early October 2026	Ubisoft says Rainbow Six Siege X crashes at launch are "related to the latest Windows Preview updates" and suggests removing them as a temporary workaround.
Early October 2026	Microsoft confirms that apps and games using AC-3 audio can fail to start or close without warning after KB5124010.
October 13, 2026	KB5127648 (builds 26100.9711, 26200.9711 and 26300.9711) fixes the AC-3 crash and a mouse stutter problem in some games.

What KB5127648 fixes for games

• AC-3 audio crashes: some apps and games that use Windows' built-in Dolby Digital (AC-3) decoder could close without warning or refuse to start after the September preview. Microsoft says older software is the most likely to use that decoder. This is fixed.
• Mouse stutter in games: mouse and camera movement could stutter in some games. Microsoft confirmed the cause was a Windows update, not your mouse or its driver. This is fixed too.

What is still open

• Rainbow Six Siege X launch crashes: Ubisoft linked them to the Windows preview updates and said it was working on a fix. As of October 14, 2026, we have not seen an announcement from Ubisoft or Microsoft saying the problem is solved.
• Battlefield 6, WARDOGS and other anti-cheat games: the crash reports came from players. Neither the reports nor Microsoft have confirmed that anti-cheat is the cause, and the October update notes do not mention anti-cheat.

What to do on your PC

1. Check your Windows version: press Win + R, type winver and note the build. A build ending in .9711 means you already have the October update.
2. Get the October update: open Settings > Windows Update and click Check for updates. It is a security update, and it fixes the AC-3 and stutter bugs above.
3. A game still crashes at launch? For Rainbow Six Siege X, Ubisoft's temporary workaround was to remove KB5124010 and KB5121794 from Settings > Windows Update > Update history. Removing KB5121794 may take a PC on 26H2 back to its previous Windows version. Pause updates afterwards and check the game's official channels before letting them come back.
4. On Windows 11 24H2 Home or Pro? October 2026 is the last security update for these editions. Move to 25H2 or 26H2 through Windows Update to keep receiving fixes.

Your PC restarts in the middle of a game?

That is a different problem. None of the issues above makes a whole PC turn off and restart: they close the game, or stop it from starting. A full restart points to a driver, the power supply, temperatures or unstable overclock settings. We explain how to find the cause in two minutes with Event Viewer in our guide: Rainbow Six Siege Restarts Your PC Mid-Game? Causes and Fixes.

Not sure what is inside your PC? Our Check My PC tool shows your graphics card and processor in seconds.

Sources: Windows Latest, Endpoint Weekly, BleepingComputer, Insider Gaming, TweakTown and Microsoft. Last checked October 14, 2026.