Windows bugs and fixes for September 14, 2026

What broke in KB5124008?

PCWorld said on September 14, 2026 that KB5124008 can stop USB audio devices working on Windows 11. The affected releases are Windows 11 versions 24H2 and 25H2, while Windows 11 version 26H1 is affected through KB5124012, according to the same PCWorld report published on September 14, 2026.

TechPowerUp said on September 13, 2026 that symptoms include This device cannot start (Code 10), silent output, unresponsive volume controls, unresponsive sound settings and missing devices in Device Manager. It is the clearest Windows 11 bug in the current update because the failure removes a basic work tool rather than changing an interface preference.

TechPowerUp said on September 13, 2026 that some devices continue working in standard stereo but fail with 8-channel or 3D audio, and some customers restored output by selecting 2-channel mode. PCWorld said on September 14, 2026 that no known workaround covered the whole problem and Microsoft was working on a resolution. Switching to 2-channel mode therefore costs multichannel output and may not restore every device. For continuity, see KB5124008 kills sound on USB Audio Class 1.0 devices on Windows 11.

Which problems still have no shipped fix?

Xda Developers said on September 12, 2026 that Microsoft had not shipped a fix for the KB5124008 Plan9 failure. The publication said folders shared to Windows through Plan9 disappear or become unreadable after installing the September 2026 security update, affecting WSL and Claude Cowork.

Applications and sandbox environments can display no Plan9 drive shares mounted, while standard Hyper-V virtual machines that do not use Plan9 remain unaffected, according to Xda Developers on September 12, 2026. Microsoft listed the failure among the Windows known issues and was working on a fix, but Xda Developers said on September 12, 2026 that no official patch or home workaround was available.

Windows Latest said on September 12, 2026 that Microsoft had also confirmed KB5124008 problems with Remote Desktop sessions. The same publication said reports linked KB5124008 to File History failing to detect external backup drives, but Microsoft had not confirmed that regression as of September 12, 2026. I would keep the distinction clear: Plan9 and Remote Desktop are confirmed, while the File History attribution remains unconfirmed. The September 8 File History entry records that separate symptom.

Which KB5120998 fixes have shipped?

BleepingComputer said on September 10, 2026 that KB5124008 fixed the mouse settings reset introduced by KB5120998. KB5120998 was the August 2026 preview update for Windows 11 versions 24H2 and 25H2, according to the BleepingComputer mouse report published on September 10, 2026.

The same report said on September 10, 2026 that non-English Windows installations could fail to load mouse personalization because of code components, causing Windows to use defaults instead. Cursor choices and cursor animations could reset, and uninstalling KB5120998 did not restore them on affected devices, according to BleepingComputer on September 10, 2026.

The BleepingComputer desktop report said on September 10, 2026 that KB5120998 could also prevent desktop settings from loading, replace the background with solid black and block manual restoration of customized settings. Microsoft said the desktop and mouse problems were resolved by KB5124008 and later updates released September 8, 2026, according to both BleepingComputer reports published September 10, 2026.

The shipped Windows update fix is therefore clear for the cursor and desktop failures: install KB5124008 or a later security update. That advice does not fix the USB audio or Plan9 regressions introduced by KB5124008.

Should KB5124008 be removed?

Windows Latest said on September 12, 2026 that KB5124008 was a mandatory Windows 11 update. Removing it may appear practical when audio, Plan9 shares or Remote Desktop stops working, but the update also contains security corrections and the shipped repairs for KB5120998.

Notebookcheck said on September 10, 2026 that the September release patched two elevation-of-privilege zero-days already exploited in the wild. Notebookcheck identified them as CVE-2026-81963 in the Windows Update Stack and CVE-2026-85880 in the Advanced Local Procedure Call component on September 10, 2026.

I treat removal as a tradeoff rather than a general fix. Windows Latest said on September 12, 2026 that KB5124008 breaks WSL-based applications and Remote Desktop sessions, while BleepingComputer said on September 10, 2026 that the same update repairs the cursor and desktop settings failures. That makes the Windows KB update problem unusually direct: removing the update would also remove its security corrections and already shipped repairs, while the cited reports do not establish uninstalling it as a fix for the affected workflows. Microsoft had not supplied a universal replacement build in the cited reports.

What can a Windows user do today?

PCWorld said on September 14, 2026 that no complete USB audio fix had shipped and Microsoft was working on a resolution. If USB audio failed after KB5124008, I would first test standard stereo or 2-channel mode because TechPowerUp said on September 13, 2026 that the change restored output for some users. The cost is the loss of 8-channel or 3D audio, and the workaround may fail.

If WSL or Claude Cowork cannot see Plan9 shares, I would not present an invented repair. Xda Developers said on September 12, 2026 that Microsoft had no official patch or home workaround, although standard Hyper-V virtual machines without Plan9 were unaffected. Waiting for a fix costs access to the affected shared-folder workflow.

If KB5120998 reset a cursor, wallpaper or desktop theme, install KB5124008 or a later security update because both BleepingComputer reports said on September 10, 2026 that updates released September 8, 2026 resolved those failures. Uninstalling KB5120998 alone was not enough for affected mouse settings, according to the BleepingComputer mouse report on September 10, 2026.

I would document the affected device, application and update before changing anything. Microsoft’s published acknowledgements separate shipped fixes from open failures, so an ordinary user can act on the exact KB and symptom rather than wait without information.