Windows KB5124010 update crashes games using AC-3 audio

Microsoft has confirmed that the September 2026 KB5124010 preview update for Windows 11 is causing some games and applications to crash. The problem affects software that relies on Windows to decode AC-3 audio, the format better known as Dolby Digital.

The company acknowledged the issue over the weekend in a Friday entry on the Windows release health dashboard, its public page for tracking known problems with Windows releases.

How the crashes show up

According to Microsoft, the symptoms vary. Some affected applications refuse to start. Others close suddenly without any warning. In a third group, the software runs normally until the user triggers a specific feature, for example playing music.

"Affected applications may vary and can include games, media players, and certain productivity applications," Microsoft said in the dashboard update.

The company stressed that the impact should be limited. Many modern applications do not hand AC-3 decoding over to Windows, so they are not affected. The component behind the crashes is mostly used by older, legacy software that still depends on the decoder built into Windows. Newer apps that support the legacy AC-3 codec often ship with their own decoding components.

Who gets the update

KB5124010 is an optional preview release. Users normally have to install it themselves by clicking the "Download and install" link in Windows Update, which should keep the number of affected machines down.

There is one exception. On Windows 11 24H2 devices where the "Get the latest updates as soon as they're available" setting is turned on, the update installs automatically. Users who enabled that option may have received the problematic build without choosing it. The release itself arrived with a long list of fixes, as covered in our report on the 46 changes in KB5124010.

Microsoft says it is working on a resolution and will share more details in a future update. It has not said when a fix will be available.

Part of a familiar pattern

This is not the first audio problem tied to Windows updates. Last month, Microsoft pushed out emergency updates to address USB audio issues, along with Remote Desktop Services failures and Hyper-V problems, after the KB5124008 and KB5124012 September 2026 security updates. Other September releases also caused black screens on AVD hosts.

Last year, in January, the company fixed a bug that caused audio playback problems and Code 10 errors on Windows 11 24H2 systems using USB audio device drivers. It also lifted a safeguard hold, a block that stops a Windows upgrade from being offered to devices with known compatibility problems. That hold had been in place because Bluetooth headsets and speakers malfunctioned on systems running Dirac audio enhancement software.

Two years ago, Microsoft confirmed a bug that pushed game audio to full volume unexpectedly on systems with USB DAC sound setups. It also blocked Windows 24H2 upgrades on PCs with incompatible Intel Smart Sound Technology (SST) audio drivers, because those systems were hitting blue screen of death (BSOD) crashes.

Our Take

For most readers, the practical advice is simple. Preview updates are optional for a reason, and this incident shows why it makes sense to keep them away from production machines. Administrators managing Windows 11 24H2 fleets should check whether the "Get the latest updates as soon as they're available" setting is enabled. It quietly turns an opt-in preview into an automatic install.

The bigger picture is a steady run of audio-related regressions across several Windows release cycles. This suggests that the audio stack, especially its legacy parts, remains a fragile area for Microsoft's testing. Organizations that still run older line-of-business or media software are the most likely to notice.

It is worth watching whether the fix lands in the next cumulative update or arrives as a separate out-of-band release, and whether Microsoft decides to apply a safeguard hold in the meantime.