Microsoft confirmed that a Windows 11 update released in September could make some apps and games crash, or fail to start, when they need to decode AC-3 audio. It has since fixed the problem in its October security update (BleepingComputer, Neowin).
<blockquote><strong>Update, October 25:</strong> Microsoft's release health dashboard now lists the issue as resolved on Windows 11 24H2, 25H2 and 26H2 in updates released on or after October 13, including the October security update KB5127648. Affected users should install the latest update, restart and test the app (<a href="https://betanews.com/article/windows-11-kb5127648-dolby-digital-crashes/">BetaNews</a>, <a href="https://windowsreport.com/windows-11-kb5127648-fixes-explorer-crashes-ac-3-audio-playback-vpn-errors-more/">Windows Report</a>).</blockquote>
| Date | Event |
|---|---|
| September 22 | Optional preview update KB5124010 released |
| October 2 | Microsoft confirms the AC-3 known issue |
| October 13 | October security update KB5127648 fixes it |
What Microsoft said
Microsoft opened a known-issue entry on its Windows release health pages on October 2 with the status Confirmed. It tied the problem to KB5124010, which carries build numbers ending in 9550 across three versions: 26100 for Windows 11 24H2, 26200 for 25H2 and 26300 for 26H2. Windows Server was not listed.
Microsoft said apps requiring AC-3 decoding, the format also known as Dolby Digital, could fail to launch, close without warning or crash when certain features are used, such as playing music, adding that "in some cases the application can fail to launch, or close without warning."
Who was likely to be hit
Older software was the most likely casualty. Applications that rely on the operating system's own AC-3 decoder were exposed, while modern apps that bundle their own decoder were unlikely to be affected. That points to games, media players and some productivity tools built years ago, though Microsoft named no specific titles.
Because KB5124010 was an optional preview, it only reached people who chose "Download and install," which limited how many machines were hit.
What you could do before the fix
Microsoft listed no workaround at the time. Windows Report suggested uninstalling the update through Settings, Windows Update, Update history, Uninstall updates, and others suggested an alternative decoder such as LAV Filters (WinTips). Uninstalling also removes the update's other fixes, so installing KB5127648 is now the better route.
A run of September problems
Windows Latest said the bug added to other problems linked to September's updates, including trouble with Remote Desktop, USB audio and File History. Preview updates are where Microsoft tests changes, and some of those tests turn up faults after they reach ordinary users. The bug appeared across 24H2, 25H2 and 26H2 at once because 26H2 is delivered as an enablement package on the same code base.
The October update has its own reported issue: KB5127648 can block some users from turning on Smart App Control.
What to watch next
Watch for any reports of AC-3 crashes persisting after KB5127648, and for Microsoft's fix for the Smart App Control issue in the October update.
