Windows 11 updates cause black screens on AVD hosts

Microsoft has confirmed that recent Windows 11 updates are stopping the desktop from loading on some systems. Affected users see a black screen after signing in.

The problem started with the August 2026 preview updates and carried into later releases, including this month's Patch Tuesday rollout. According to Microsoft, it mainly hits Azure Virtual Desktop (AVD) hosts that use FSLogix. AVD is Microsoft's cloud-based desktop and app virtualization service. FSLogix is a tool that speeds up the loading of user profiles in virtual desktop environments.

Which updates are involved

Microsoft lists the following updates as linked to the issue:

• KB5120996 for Windows 11, version 26H1
• KB5120998 for Windows 11, versions 24H2 and 25H2
• KB5124008 and KB5122880, released on this month's Patch Tuesday

The most common symptom is a black screen right after sign-in. The desktop stays out of reach until the user starts the session manually. Admins who check the application event logs may also find entries showing that Windows Explorer crashed.

A permanent fix is not yet available. Until one ships, Microsoft suggests starting Windows Explorer by hand:

1. Press Ctrl+Shift+Esc to open Task Manager.
2. Select Run new task.
3. Type explorer.exe and click OK.

This brings the desktop back for the current session. It does not remove the cause.

Known Issue Rollback for enterprise devices

For managed business environments, Microsoft has pushed a mitigation through Known Issue Rollback (KIR). This Windows feature can undo a specific faulty change delivered through Windows Update without uninstalling the whole update.

IT administrators can deploy the fix through Group Policy using the package that matches their Windows version:

• Windows 11, version 26H1: KB5124006 Known Issue Rollback
• Windows 11, versions 25H2 and 24H2: KB5124010 Known Issue Rollback

"You will need to install and configure the Group Policy for your version of Windows to resolve this issue. You will also need to restart your device(s) to apply the group policy setting," Microsoft said.

The company also pointed out that the policy is temporary. "Note that this Group Policy will disable the change causing this issue until a resolution is released in a future Windows update," it explained.

Microsoft's support website has more detail on how to deploy and configure KIR group policies.

Not the first problem with KB5120998

This is not the first bug tied to the August optional update KB5120998. Earlier in September, Microsoft fixed separate known issues in which the same update wiped mouse and desktop settings on some Windows 11 machines.

Two unrelated problems in a single optional release, both hitting the basic desktop experience, will not reassure administrators who manage large fleets of Windows devices.

Our Take

For most home users, this bug probably won't matter much. The main impact is on organizations that run virtual desktops on Azure with FSLogix profile management. That setup is common in enterprises and in managed service providers. A black screen at sign-in on shared virtual desktops can quickly turn into a flood of help desk tickets. The manual Task Manager workaround works for one user but does not scale well across hundreds of sessions.

The KIR route is the more practical option for these teams. It is worth noting, however, that it needs Group Policy changes and a device restart. On AVD host pools, restarts have to be scheduled around active user sessions.

The bigger concern is what this does to patching discipline. Every faulty update gives admins another reason to hold back Windows patches, and that delay has a cost. This month alone, flaws such as the Check Point VPN remote code execution bug and a TeamCity vulnerability now abused by ransomware gangs show how quickly attackers move once a patch is public. The sensible response is not to skip updates. Teams should test them first on a small group of hosts, especially in virtual desktop environments. Preview releases, like the August update that started this problem, are better kept out of production altogether.

It is worth watching whether Microsoft's permanent fix lands in the October updates, and whether KB5120998 turns up any more side effects. After the mouse and desktop settings bugs, this is the latest issue in a run of problems traced back to the same release.