On September 24, Microsoft reported an issue affecting devices that installed the August 27 preview update for Windows 11. Users are encountering a black screen after sign-in, which prevents the desktop from loading correctly. This problem primarily affects Azure Virtual Desktop (AVD) hosts utilizing FSLogix, particularly with existing user profiles. In response, Microsoft has issued interim workarounds while a permanent solution is being developed for a future Windows Update.
Affected Scope and Causal Update
According to Microsoft’s release health dashboard, the details surrounding the issue are as follows:
| Item | Details |
|---|---|
| Affected OS | Windows 11 versions 26H1 / 25H2 / 24H2 (client) |
| Causal update | KB5120998 (non-security preview released August 27, 2026; OS Build 26200.9278) |
| Primary symptom | Black screen after sign-in; desktop session does not load automatically |
| Environments most affected | Azure Virtual Desktop (AVD) hosts using FSLogix; existing user profiles |
| Microsoft status | Mitigated; permanent fix to be delivered in a future update |
As Windows updates are cumulative, the problematic changes from the preview update have persisted into the monthly security update (KB5124008) released on September 8. Consequently, even systems that did not apply the preview update may experience similar issues if they have installed subsequent monthly updates. Microsoft officially acknowledged this known issue on September 24, noting that explorer.exe crashes might be logged in the application event log.
Two Interim Workarounds
For users facing this issue, two interim workarounds have been suggested:
- Manual Desktop Launch: From the black screen, users can press Ctrl+Shift+Esc (or navigate through Ctrl+Alt+Delete) to open Task Manager. From there, they can select “Run new task” from the File menu, type explorer.exe, and execute it to force the desktop to load.
- Known Issue Rollback (KIR): Microsoft has initiated a rollback of the specific change causing the problem. For internet-connected Windows 11 devices, a partial rollback will be automatically delivered within 24 hours, providing a temporary resolution.
However, it’s important to note that KIR is automatically distributed only to non-enterprise devices that are not centrally managed by IT departments. For enterprise-managed devices, administrators must manually deploy the KIR policy definition (.msi) provided by Microsoft, configure it as a Group Policy, and restart the device.
- For Windows 11 version 26H1: KB5124006 260924_20071 Known Issue Rollback
- For Windows 11 versions 25H2 / 24H2: KB5124010 260924_20021 Known Issue Rollback
Policy propagation typically takes 90–120 minutes under the default Group Policy refresh interval, but running “gpupdate” on affected devices can expedite confirmation. Interestingly, setting the policy to “Disabled” is what actually enables the rollback, with the causal change being disabled only after the policy is applied and the device is restarted.
A String of Windows 11 Update Problems
This black screen issue adds to a growing list of update-related challenges for Windows 11 throughout 2026. Observers have noted that the January update KB5074109 led to black screens, configuration errors in Outlook, authentication failures in AVD, and other complications, including blue screens and boot failures on certain PCs.
Subsequent updates have also caused a range of issues, including:
- March 2026: KB5079473 broke Microsoft account sign-ins, impacting Teams, OneDrive, Edge, and Office, resolved 11 days later by an out-of-band update.
- April 2026: KB5083769 triggered BitLocker recovery screens, necessitating multiple reboots.
- June 2026: KB5094126 caused boot failures and BitLocker recovery loops on HP business PCs.
- July 2026: KB5101650 resulted in unexpected shutdowns and battery drain on Dell business PCs, leading to Microsoft blocking the update.
- September 2026: KB5124008 introduced issues such as Remote Desktop failures and USB audio anomalies, prompting an emergency update that has yet to resolve all concerns.
Stability Gap with Windows 10 Becomes Clear
In contrast, Windows 10 has experienced significantly fewer issues over the same period. Of the nine monthly updates from January to September 2026, only three months reported notable problems. The January update caused shutdown failures, but this was swiftly addressed in February. Subsequent updates in February and March proceeded without incident, and while June and July faced some glitches, the impact was minimal.
Windows 10’s support has been extended until October 2027 for consumer devices, with a separate paid offering for business PCs available until October 2028. As enterprise IT administrators navigate these challenges, identifying affected devices and ensuring proper configuration of KIR policies will be essential to mitigate disruptions and maintain operational efficiency.
