Microsoft has confirmed a new Windows 11 issue that can cause some applications to close unexpectedly after installing update KB5124010 or later updates. The problem affects software that relies on Windows to decode AC-3 audio, commonly known as Dolby Digital, and applies to Windows 11 versions 24H2, 25H2 and 26H2. Microsoft says it is working on a resolution for a future Windows update, but no fix has been released yet.
The issue originated with KB5124010, the September 22, 2026 non-security preview update for Windows 11. Microsoft says that after installing the update or subsequent Windows updates, some applications requiring AC-3 audio decoding may unexpectedly close. Depending on what the application is doing, affected software can fail to launch, shut down without warning or work normally until a feature involving audio playback is triggered.
Microsoft explains that the affected component is most commonly used by legacy applications that depend on Windows’ built-in audio decoding rather than shipping their own decoder. That means the issue is more likely to surface in older games, media software and productivity applications using the legacy Windows audio path. Many modern applications include their own decoding components and therefore are not expected to encounter this particular problem.
KB5124010 applies to Windows 11 versions 24H2, 25H2 and 26H2, with Microsoft listing OS builds 26100.9550, 26200.9550 and 26300.9550 respectively. The company currently lists those three client versions as affected, while Windows Server is not included among the affected platforms. The update itself also contained a range of other Windows improvements, including Bluetooth audio reliability changes, Settings fixes and accessibility updates.
The AC-3 problem is separate from another recent Windows 11 audio issue involving USB Audio Class 1.0 hardware. That earlier bug, associated with the September 8 security update, could prevent some USB audio devices from starting, produce no sound or cause Device Manager Code 10 errors. Microsoft has already mitigated portions of that problem through an out-of-band update, while the newer AC-3 application-crash issue remains unresolved.
Microsoft has not published an official workaround for the AC-3 regression. Its current guidance says a resolution is being prepared for a future Windows update and that additional information will be provided when available. Users who experience unexplained crashes in older software after installing KB5124010 should therefore consider whether the affected application uses Windows’ built-in Dolby Digital decoding before assuming the failure is related to hardware or a broader audio problem.
The issue adds another compatibility problem to Microsoft’s recent Windows update cycle. The company has also been addressing unrelated problems involving USB audio hardware, virtual desktop sessions and domain authentication, while a separate Microsoft Defender update recently fixed false antivirus warnings that incorrectly told users their protection was disabled. In each case, the underlying software continued to function differently from what the warning or symptom initially suggested, making Microsoft’s release-health documentation particularly important for diagnosing recent Windows problems.
For KB5124010 specifically, the impact appears limited to applications using the affected legacy decoding path rather than Windows audio as a whole. Users should not expect every program capable of playing AC-3 content to crash, since applications with their own decoding implementations can avoid the Windows component involved. Microsoft has not given a date for the corrective update, so affected users and administrators will need to watch for an updated Windows release-health notice or a future cumulative update containing the fix.
