What is the quickest workaround for a user stuck on a black screen?

Microsoft's user-level workaround: open Task Manager (Ctrl+Shift+Esc), select Run new task, enter explorer.exe, and select OK. Microsoft describes this as a temporary mitigation, so it has to be repeated if the symptom returns at the next sign-in.

Does the Known Issue Rollback remove the update?

No. Microsoft's KIR documentation says a KIR rolls back a specific change from a nonsecurity update while all other changes in that release remain intact, and that the rollback is temporary. Microsoft's known-issue entry adds that the Group Policy disables the change causing this issue until a resolution ships in a future Windows update, and that devices must restart to apply it.

How do I know when this is fixed?

Watch the known-issue entry on the Windows 11 release-health page for your version. Resolved issues move to a Resolved state with a resolution note; as of the last update, September 29, 2026, Microsoft says only that it is working on a resolution to be released in a future Windows update.

Blog · 3 min read · October 5, 2026

AVD + FSLogix black screen after sign-in: KB5120998

Microsoft opened this Windows 11 known issue September 25, 2026 at 19:38 PT and lists it Mitigated as of September 29, 2026 at 10:12 PT. A Known Issue Rollback Group Policy is available; the permanent fix is promised in a future Windows update, with no date.

If your Azure Virtual Desktop pool uses FSLogix and users report a black screen after sign-in, check your hosts' update history before rebuilding profiles. Microsoft has a known issue tied to the August 2026 non-security preview update (KB5120998) and later updates. Here is the triage order we would use.

Status as of October 5, 2026: Mitigated, not Resolved. Opened September 25, 2026 at 19:38 PT. Last updated September 29, 2026 at 10:12 PT. Microsoft's page prints all times in PT.

What Microsoft says

Microsoft's entry, "Devices might experience a black screen or desktop loading issues after sign-in," lists the originating update as KB5120998 (OS Build 26200.9278, August 27, 2026). Its description reads: "some devices might experience desktop loading issues. This issue has been primarily observed on Azure Virtual Desktop (AVD) hosts, using FSLogix. This issue appears to occur more frequently with some existing user profiles."

The listed symptoms are:

A black screen appears after sign-in and the desktop session does not load automatically.
Users might be unable to access their desktop until the desktop session is started manually.
Application event logs might show Windows Explorer crashes.

Affected platforms, as printed: Client: Windows 11, version 26H2; Windows 11, version 26H1; Windows 11, version 25H2; Windows 11, version 24H2. Server: None. We read the 25H2 page only.

Step 1: Confirm you match the pattern

Check all three before you change anything. They come from Microsoft's description.

Session hosts run Windows 11 24H2, 25H2, 26H1 or 26H2 with KB5120998 or later installed.
Users get a black screen after sign-in and the desktop does not load on its own.
The Application event log shows Windows Explorer crashes.

Microsoft adds that the issue appears more often with some existing profiles. It does not say what makes those profiles different.

Step 2: Give users the workaround now

Microsoft's user-level workaround: open Task Manager (Ctrl+Shift+Esc), select Run new task, enter explorer.exe, and select OK. Microsoft calls this a temporary mitigation. Give it to your help desk now, because the rollback needs a restart.

Step 3: Apply the Known Issue Rollback

Microsoft's entry says to install and configure a special Group Policy for your version of Windows, then restart the devices. The policy appears under Computer Configuration > Administrative Templates. The downloads, with the names Microsoft prints:

Windows 11, version 26H1: KB5124006 260924_20071 Known Issue Rollback
Windows 11, version 26H2, 25H2 and 24H2: KB5124010 260924_20021 Known Issue Rollback

The download file name for the 26H2/25H2/24H2 package also mentions Windows Server 2025, even though the known-issue entry lists Server as None. Check the file name against your host OS before you deploy.

Microsoft's KIR deployment article covers the domain mechanics:

Run the matching .msi on your Group Policy management machine. It installs the policy definition. With a Central Store, copy the .admx and .adml files there.
Create a GPO and link it to the OU that holds your session hosts.
Under Computer Configuration > Administrative Templates, open the KIR policy, then select Edit > Disabled > OK. Disabled is what activates the KIR.
Wait for policy refresh (Microsoft says 90 to 120 minutes by default) or run gpupdate, then restart each host.

The same article describes an Intune path using custom ADMX ingestion, and says the policy definition can be removed once Microsoft publishes a corrected update.

Microsoft states the change is disabled only after the device applies the policy and restarts.

Step 4: Watch for Resolved

The entry says: "We are working on a resolution for this issue, and it will be released in a future Windows update." No update or date is named. Check the release-health page for your version for the entry to move from Mitigated to Resolved. Until then, give the KIR GPO an owner and a review date.

Sources

If you want a senior engineer to check your AVD host pool and profile setup, the project intake form takes about three minutes. We'll come back with scope and a fixed-fee range.

Pro IT NW does senior-led Microsoft infrastructure work for mid-market and regulated organizations. Vendor-neutral, labor-only. This post reflects Microsoft's published documentation as of October 5, 2026, plus our own judgment on sequencing, not Microsoft's guidance.

Questions we get asked

Which Windows versions does the KB5120998 black screen affect?: Per Microsoft's Windows 11, version 25H2 release-health page, the affected platforms are Client: Windows 11, version 26H2; Windows 11, version 26H1; Windows 11, version 25H2; Windows 11, version 24H2. Server: None. Microsoft says the issue has been primarily observed on Azure Virtual Desktop (AVD) hosts using FSLogix.
What is the quickest workaround for a user stuck on a black screen?: Microsoft's user-level workaround: open Task Manager (Ctrl+Shift+Esc), select Run new task, enter explorer.exe, and select OK. Microsoft describes this as a temporary mitigation, so it has to be repeated if the symptom returns at the next sign-in.
Does the Known Issue Rollback remove the update?: No. Microsoft's KIR documentation says a KIR rolls back a specific change from a nonsecurity update while all other changes in that release remain intact, and that the rollback is temporary. Microsoft's known-issue entry adds that the Group Policy disables the change causing this issue until a resolution ships in a future Windows update, and that devices must restart to apply it.
How do I know when this is fixed?: Watch the known-issue entry on the Windows 11 release-health page for your version. Resolved issues move to a Resolved state with a resolution note; as of the last update, September 29, 2026, Microsoft says only that it is working on a resolution to be released in a future Windows update.

Related service

VMware Exit & Server Modernization

Written by the team at Pro IT NW · Senior-led Microsoft project consultancy · Seattle and the Pacific Northwest, delivered USA-wide.

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