Microsoft has confirmed that the optional KB5124010 preview update for Windows 11 is causing crashes in applications that use AC-3 (Dolby Digital) audio decoding through Windows’ built-in components.
According to a Friday update on the Windows release health dashboard, affected applications may fail to launch entirely, close unexpectedly, or appear to run normally until a specific feature, such as music playback, is triggered. Microsoft says the impact can extend across games, media players, and certain productivity applications.
Who Is Affected
KB5124010 is an optional update, meaning most users would need to manually click “Download and install” to get it. However, it installs automatically on Windows 11 24H2 devices that have the “Get the latest updates as soon as they’re available” setting enabled, which widens the pool of potentially affected machines.
Microsoft notes that many modern applications are not impacted because they ship their own audio decoding components rather than relying on the legacy Windows AC-3 codec. The bug is most likely to surface in older, legacy applications that still depend on Windows’ built-in audio decoding path.
No Fix Timeline Yet
Microsoft says it is working on a resolution but has not provided an estimated timeline. The company says it will share further details in a future update to the release health dashboard.
Part of a Rocky Patch Cycle
This is the latest in a string of audio-related problems tied to Microsoft’s September 2026 update wave. Last month, the company issued emergency fixes for USB audio issues, Remote Desktop Services failures, and Hyper-V problems stemming from the KB5124008 and KB5124012 security updates.
Microsoft has dealt with similar audio regressions before. In January of last year, it fixed a bug causing audio playback issues and Code 10 errors on Windows 11 24H2 systems with USB audio drivers, and separately lifted a safeguard hold affecting Bluetooth headsets and speakers on systems running Dirac audio improvement software. Two years ago, the company also addressed an issue where game audio would unexpectedly jump to full volume on USB DAC sound systems.
Security teams managing Windows 11 24H2 fleets should check whether automatic preview update delivery is enabled and monitor for application crashes tied to legacy audio playback until Microsoft issues a fix.