Windows 11 KB5124010 update crashes apps using AC-3 audio
Microsoft confirms the optional September 2026 KB5124010 preview update for Windows 11 causes crashes in some games and applications that use AC-3 audio decoding.
Microsoft confirmed that the September 2026 KB5124010 Windows 11 preview update causes crashes in some games and applications using AC-3 (Dolby Digital) audio decoding. After installing the update, affected software may close unexpectedly when it attempts to decode Dolby AC-3 data streams.
In some cases, apps crash upon startup or close without warning. In other cases, they function normally until specific audio features are used, such as playing music, increasing volume, or changing audio settings. Microsoft admitted the bug leads to the unexpected closing of games and apps. Whether a crash occurs depends entirely on the actions the application performs.
Affected apps and root cause
The issue impacts legacy apps and games relying on Windows’ built-in AC-3 audio decoding, while modern apps with their own decoders remain unaffected. The problematic code component is most commonly used in older applications that depend on the audio decoding integrated into Windows.
Microsoft has not disclosed an exact list of affected titles. "Affected applications may vary and can include games, media players, and certain productivity applications," Microsoft said. Many modern applications are not affected because they do not rely on Windows to process this encoding, instead using their own audio decoding components. This includes many modern apps that use the outdated AC-3 codec but bundle their own decoders.
Update details and Microsoft response
The optional KB5124010 update was released on September 22, 2026. It installs automatically only on devices where the 'Get the latest updates as soon as they're available' setting is enabled; otherwise, users must manually select 'Download and install'. The update was intended to fix File History issues, though testing showed backup problems persisted.
The bug affects multiple Windows 11 versions, as shown in the table below.
| Windows 11 Version | Affected by KB5124010 Bug |
|---|---|
| 26H2 | Yes |
| 25H2 | Yes |
| 24H2 | Yes |
Microsoft acknowledged the audio-decoding problem in its Windows Release Health notes. The company stated it is working on a resolution but has not provided an estimated timeline for a fix. It will share more information in a future update.
This audio crash issue is separate from a separate September USB audio bug that caused devices to stop producing sound or generated Code 10 errors. Microsoft confirmed it is addressing multiple known issues, including problems with Remote Desktop and File History backups, and is using AI to deploy hundreds of fixes. Microsoft is working on a resolution and will share more information in a future update.
