Windows 11 Black Screen After Sign-In? Microsoft Confirms the KB5120998 Bug: How to Get Your Desktop Back (2026)

You type your PIN, the welcome animation spins, and then nothing. No taskbar. No icons. Sometimes a mouse cursor floating on black.

Microsoft has an open known issue that looks exactly like this. But it isn’t the only cause, and treating every black screen as “the update bug” leads people to uninstall updates they didn’t need to touch.

Here’s how to get your desktop back in under a minute, then figure out which problem you actually have.

Contents

• Is the Windows 11 Black Screen After Sign-In a Known Microsoft Bug?
• How Do You Get the Desktop Back Right Now?
• Which Black Screen Do You Have?
• Does This Bug Affect Home PCs, or Only Work Computers?
• What Should IT Admins Do About KB5120998?
• Should You Uninstall the Update?
• Tips
• Warnings
• FAQ
• Sources

Is the Windows 11 Black Screen After Sign-In a Known Microsoft Bug?

Yes. Microsoft confirmed on September 25, 2026 that some Windows 11 devices show a black screen or fail to load the desktop after sign-in following the August 27, 2026 preview update KB5120998 and later updates, according to the Windows 11 release health page.

The issue is listed for Windows 11 versions 24H2, 25H2, 26H1, and 26H2. No Windows Server versions are listed. Its status is “Mitigated,” which means there’s a workaround but not yet a permanent fix.

Microsoft lists three symptoms:

• A black screen appears after sign-in and the desktop doesn’t load on its own.
• You can’t reach your desktop until the session is started manually.
• The Application event log shows Windows Explorer crashes.

When I checked the entry’s wording, I noticed that Microsoft says the problem “appears to occur more frequently with some existing user profiles.” That detail matters later, because it’s the clue that separates this bug from a driver problem.

How Do You Get the Desktop Back Right Now?

On a Windows 11 PC stuck on a black screen after sign-in, restarting Windows Explorer from Task Manager restores the taskbar and desktop in most cases, and it’s the first workaround Microsoft lists for the KB5120998 issue.

1. Press Ctrl+Shift+Esc. Task Manager should open even on a black screen.
2. Select “Run new task.” It’s at the top of the Processes page.
3. Type explorer.exe and press OK. Your taskbar and desktop icons should appear within a few seconds.
4. If Task Manager doesn’t open, press Ctrl+Alt+Delete and choose Task Manager from that screen instead.
5. If you see nothing at all, not even a cursor, press Win+Ctrl+Shift+B. That shortcut restarts the graphics driver. You’ll hear a beep and the screen will flash.

Honestly, step 3 fixes it for most people. It’s not a permanent repair, though. You may need to repeat it at the next sign-in until Microsoft ships a fix.

Which Black Screen Do You Have?

What you see on the black screen tells you a lot. Use this table before you start uninstalling anything.

Table: our triage guide built from Microsoft’s known-issue symptoms and standard Windows troubleshooting, checked October 8, 2026.

Most people skip the “one account or all accounts?” test. It takes two minutes and tells you whether to look at the profile or the whole system.

If your problem is sound rather than video, a different September update bug may be involved. Our guide to apps crashing after KB5124010 because of the AC-3 audio bug covers that one.

Does This Bug Affect Home PCs, or Only Work Computers?

Microsoft says the Windows 11 black-screen-after-sign-in issue from KB5120998 has been seen mainly on Azure Virtual Desktop hosts that use FSLogix profile containers, so a typical home PC with a local account is less likely to be hit by this specific bug.

FSLogix is a Microsoft tool that loads user profiles from network storage in virtual desktop setups. You almost certainly don’t have it at home.

That doesn’t mean home users are immune. Microsoft lists the consumer Windows 11 versions as affected, and “primarily observed” isn’t “only.” I found that early reports on forums and tech news sites mix both cases together, which is why so many home users assume they’ve got the update bug when it’s really a driver.

A good rule: if explorer.exe brings your desktop back every time, and it started after late-August updates, it’s probably this bug. If explorer.exe does nothing, look elsewhere.

What Should IT Admins Do About KB5120998?

IT administrators can mitigate the KB5120998 black-screen issue on managed Windows 11 devices by installing and configuring Microsoft’s Known Issue Rollback Group Policy for their Windows version and then restarting the devices, as described on the Windows release health page.

• Windows 11 26H1: the policy is named “KB5124006 260924_20071 Known Issue Rollback.”
• Windows 11 24H2, 25H2, and 26H2: the policy is named “KB5124010 260924_20021 Known Issue Rollback.”
• After installing the MSI, find the setting under Computer Configuration > Administrative Templates, enable it, and restart.

Microsoft’s guide to deploying a Known Issue Rollback walks through the Group Policy steps. The rollback disables only the change that causes the problem, so you keep the security fixes.

Home and Pro users not managed by IT don’t need to do this. Known Issue Rollbacks normally reach unmanaged home devices automatically through Windows Update, which can take a day or so and a restart.

Should You Uninstall the Update?

Uninstalling the latest Windows 11 cumulative update is usually the wrong first move for this black screen, because the issue began with KB5120998 in August and carries into later updates, so removing only the newest one may not help while it does remove security fixes.

The timeline matters. KB5120998 was the August 27 preview. Since then you’ve likely installed the September 8 security update and maybe the September 22 preview KB5124010. Rolling back one step won’t get you to a pre-August build.

A better order of operations:

1. Use the explorer.exe workaround at each sign-in.
2. Restart once a day so the automatic rollback has a chance to land.
3. Install October’s updates when they arrive and check whether the issue is marked resolved.

Also keep the calendar in mind. Windows 11 24H2 Home and Pro stop getting updates on October 13, 2026, so a fix won’t reach that version after that date. See our guide to moving off 24H2 before support ends.

Tips

• Create a second local admin account now. If one profile breaks, you’ll have a way in.
• Pin Task Manager to your memory: Ctrl+Shift+Esc works even when the taskbar doesn’t.
• Check Event Viewer > Windows Logs > Application for “explorer.exe” errors. That’s Microsoft’s own sign of this bug.
• If you’re on a work laptop, report it rather than fixing it yourself. IT may already have the rollback policy ready.

Warnings

• Don’t run registry “fixes” from random videos. Microsoft hasn’t published a registry workaround for this issue.
• Don’t reset your PC as a first step. The explorer.exe workaround is reversible, a reset isn’t.
• If the screen stays black even in Safe Mode, it’s not this bug. Suspect hardware or the display driver.
• Known-issue status can change. Check the release health page before assuming October’s update fixed it.

FAQ

Why does the black screen come back every time I restart?

The explorer.exe workaround only fixes the current session. Until Microsoft ships a permanent fix or the rollback applies to your PC, Explorer can fail again at the next sign-in.

Is the Windows 11 black screen after sign-in caused by a virus?

Usually not. A black screen with a working mouse cursor is far more often a crashed Explorer process or a display driver problem. Run a full Microsoft Defender scan after your desktop is back if you want to rule it out.

Does the KB5120998 black screen affect Windows 10?

No. Microsoft lists only Windows 11 versions 24H2, 25H2, 26H1, and 26H2 as affected by this known issue.

Sources

• Microsoft Learn — Windows 11, version 24H2 known issues and notifications
• Microsoft Support — August 27, 2026 KB5120998 preview update
• Microsoft Learn — Use Group Policy to deploy a Known Issue Rollback

Fact-checked against Microsoft’s Windows release health documentation as of October 8, 2026. Known-issue status and workarounds can change with each monthly update.