August 20, 2020—KB4566116 (OS Builds 18362.1049 and 18363.1049) Preview

IMPORTANT Starting in July 2020, we will resume non-security releases for Windows 10 and Windows Server, version 1809 and later. There is no change to the cumulative monthly security updates (also referred to as the "B" release or Update Tuesday release). For more information, see the blog post Resuming optional Windows 10 and Windows Server non-security monthly updates.

IMPORTANT Starting in July 2020, all Windows Updates will disable the RemoteFX vGPU feature because of a security vulnerability. For more information about the vulnerability, seeCVE-2020-1036 and KB4570006. After you install this update, attempts to start virtual machines (VM) that have RemoteFX vGPU enabled will fail, and messages such as the following will appear:

If you re-enable RemoteFX vGPU, a message similar to the following will appear:

“The virtual machine cannot be started because all the RemoteFX-capable GPUs are disabled in Hyper-V Manager.”
“The virtual machine cannot be started because the server has insufficient GPU resources.”

"We no longer support the RemoteFX 3D video adapter. If you are still using this adapter, you may become vulnerable to security risk. Learn more (https://go.microsoft.com/fwlink/?linkid=2131976)”

What's new for Windows 10, version 1909 and Windows 10, version 1903 release notes

Windows 10, versions 1903 and 1909 share a common core operating system and an identical set of system files. As a result, the new features in Windows 10, version 1909 were included in the recent monthly quality update for Windows 10, version 1903 (released October 8, 2019), but are currently in a dormant state. These new features will remain dormant until they are turned on using an enablement package, which is a small, quick-to-install “master switch” that simply activates the Windows 10, version 1909 features.

To reflect this change, the release notes for Windows 10, version 1903 and Windows 10, version 1909 will share an update history page. Each release page will contain a list of addressed issues for both 1903 and 1909 versions. Note that the 1909 version will always contain the fixes for 1903; however, 1903 will not contain the fixes for 1909. This page will provide you with the build numbers for both 1909 and 1903 versions so that it will be easier for support to assist you if you encounter issues.

For more details about the enablement package and how to get the feature update, see the Windows 10, version 1909 delivery options blog.

For more information about the various types of Windows updates, such as critical, security, driver, service packs, and so on, please see the following article.

Note Follow @WindowsUpdate to find out when new content is published to the release information dashboard.

Highlights

Updates an issue that causes the hard drive to fill up in certain error situations.
Updates an issue that prevents Microsoft Gaming Services from starting because of error 15612.
Updates time zone information for the Yukon, Canada.
Updates a visual offset issue on a touchscreen. Edits you make with a pen or finger appear in a different region than expected if the device is connected to an external monitor.
Updates an issue that causes the Settings page to close unexpectedly, which prevents default applications from being set up properly.
Updates an issue that prevents you from unlocking a device if you typed a space before the username when you first signed in to the device.
Updates an issue that causes applications to take a long time to open.

Improvements and fixes

This non-security update includes quality improvements. Key changes include:

This build includes all the improvements from Windows 10, version 1903.
No additional issues were documented for this release.

This non-security update includes quality improvements. Key changes include:

Addresses an issue with pinned Add-ins that cause Microsoft Outlook to become unresponsive.
Provides the ability to sync the Microsoft Edge IE Mode unidirectional session cookie when an administrator configures the session cookie.
Addresses an issue that causes the hard drive to fill up in certain error situations.
Addresses an issue that prevents Microsoft Gaming Services from starting because of error 15612.
Addresses an issue that prevents Visual Basic 6.0 (VB6) applications from using ListView in MSCOMCTL.OCX after upgrading to Windows 10, version 1903 and later.
Addresses a runtime error that causes VB6 to stop working when duplicate windows messages are sent to WindowProc().
Addresses an issue that displays a black screen to Windows Virtual Desktop (WVD) users when they attempt to sign in.
Updates time zone information for the Yukon, Canada.
Addresses an issue that prevents the deletion of Notification State registries for certain apps even after the user profile is deleted.
Addresses an issue that causes an application that uses msctf.dll to stop working, and the 0xc0000005 (Access violation) exception appears.
Addresses a visual offset issue on a touchscreen. Edits you make with a pen or finger appear in a different area than expected if the device is connected to an external monitor.
Addresses an issue that prevents Cortana Smart lighting from working as expected if you shut down the machine while Fast Shutdown is enabled.
Addresses an issue that causes new child windows to flicker and appear as white squares on server devices that are configured for stark visual contrast.
Addresses an issue that causes the Settings page to close unexpectedly, which prevents default applications from being set up properly.
Addresses an issue with File Explorer’s preview of .msg files when Microsoft Outlook 64-bit is installed.
Addresses an issue that causes all open Universal Windows Platform (UWP) apps to close unexpectedly. This occurs when their installer calls the Restart Manager to restart File Explorer (explorer.exe).
Addresses an issue that prevents Windows 8.1 apps from projecting to a secondary display when those apps use the StartProjectingAsync API.
Addresses an issue that causes user profile folder names to get excessively long, which might lead to MAX_PATH issues.
Addresses an issue that prevents a delegated user from importing a Group Policy object (GPO) even though the user has the required privilege.
Addresses an issue that causes the Event Viewer Microsoft Management Console (MMC) to stop working when the secondary monitor is above the primary monitor. An out of bounds exception appears.
Addresses an issue that sends a high volume of events during a real-time session in a short period of time.
Addresses an issue with object performance counters.
Addresses an issue that causes an error if you open Microsoft OneDrive files on demand when User Experience Virtualization (UE-V) is enabled. To apply this solution, set the following DWORD to 1: “HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\UEV\Agent\Configuration\ApplyExplorerCompatFix”
Addresses an issue that causes the promotion of a server to a domain controller to fail. This occurs when the Local Security Authority Subsystem Service (LSASS) process is set as Protected Process Light (PPL).
Addresses an issue in which AppLocker publisher rules might sometimes prevent applications from loading software modules; this can cause partial application failure.
Addresses an issue that sometimes prevents AppLocker from running an application whose publisher rule allows it to run.
Addresses an issue that generates a “Sync stopped, Can't encrypt files” error when users attempt to sync their Work Folder. This issue occurs after you configure encrypted Work Folders on the client.
Addresses an issue that causes the memory cache to increase without boundaries when an application calls the CryptCATAdminCalcHashFromFileHandle() function. With this update, cached memory usage is now limited. Cached memory will not be released until the process ends.
Addresses an issue that prevents you from unlocking a device if you typed a space before the username when you first signed in to the device.
Addresses an issue that causes applications to take a long time to open.
Addresses an issue that causes a system to stop working and generates a 7E stop code.
Addresses classification failures caused by the wrong User Principal Name (UPN).
Addresses an issue with a sleep system call on Glibc-2.31 or later that’s running on a Windows Subsystem for Linux 1 (WSL 1) distribution.
Adds support for WSL 2; for more information, see WSL 2 Support is coming to Windows 10 Versions 1903 and 1909.
Addresses an issue that might display Processor Frequency as zero (0) for certain processors.
Addresses an issue that causes delays during shutdown when running the Microsoft Keyboard Filter Service.
Addresses an issue that prevents a host’s virtual private network (VPN) connection from sharing with virtual machines (VM) connected to the Default Switch.
Addresses an issue with sourcing the root domain directory partition of a global catalog from a child domain controller (DC) when promoting, unhosting, or rehosting the DC. This might cause LSASS to consume all the available memory on the child DC. This issue is specific to Active Directory forests that contain 100 or more domain controllers.
Addresses an issue that fails to log events 4732 and 4733 for Domain-Local group membership changes in certain scenarios. This occurs when you use the “Permissive Modify” control; for example, the Active Directory (AD) PowerShell modules use this control.
Addresses an issue that might prevent the cluster service from starting and generates the error “2245 (NERR_PasswordTooShort)”. This occurs if you configure the “Minimum Password Length” Group Policy with more than 14 characters. For more information, see KB4557232.
Addresses an issue that causes the configuration of the “Minimum Password Length” Group Policy with more than 14 characters to have no effect. For more information, see KB4557232.
Addresses an issue that causes the loss of written data when an application opens a file and writes to the end of the file in a share folder.
Addresses an issue with Server Message Block (SMB). This issue incorrectly logs the Microsoft-Windows-SMBClient 31013 event in the Microsoft-Windows-SMBClient/Security event log of an SMB client when an SMB server returns STATUS_USER_SESSION_DELETED. This issue occurs when SMB client users or applications open multiple SMB sessions using the same set of Transmission Control Protocol (TCP) connections on the same SMB Server. This issue most likely occurs on Remote Desktop Servers.
Addresses an issue that prevents modern applications from opening because of a race condition during automatic updates. As a result, the appx package has a reduced or zero byte file size.

If you installed earlier updates, only the new fixes contained in this package will be downloaded and installed on your device.

Windows Update Improvements

Microsoft has released an update directly to the Windows Update client to improve reliability. Any device running Windows 10 configured to receive updates automatically from Windows Update, including Enterprise and Pro editions, will be offered the latest Windows 10 feature update based on device compatibility and Windows Update for Business deferral policy. This doesn't apply to long-term servicing editions.

Known issues in this update

Symptom

Workaround

When updating to Windows 10, version 1903 or Windows 10, version 1909 from any previous version of Windows 10, you might receive a compatibility report dialog with "What needs your attention" at the top and the error, "Continuing with the installation of Windows will remove some optional features. You may need to add them back in Settings after the installation completes." You might receive this compatibility warning when LOCAL SYSTEM accounts are blocked in a firewall from accessing the internet via HTTP. This is caused by the Windows 10 Setup Dynamic Update (DU) being unable to download required packages.

This issue is resolved in KB4579919.

How to get this update

Before installing this update

Microsoft strongly recommends you install the latest servicing stack update (SSU) for your operating system before installing the latest cumulative update (LCU). SSUs improve the reliability of the update process to mitigate potential issues while installing the LCU. For general information about SSUs, see Servicing stack updates and Servicing Stack Updates (SSU): Frequently Asked Questions.

If you are using Windows Update, the latest SSU (KB4569073) will be offered to you automatically. To get the standalone package for the latest SSU, search for it in the Microsoft Update Catalog.

Install this update

Release Channel	Available	Next Step
Windows Update or Microsoft Update	Yes	Go to Settings > Update & Security > Windows Update. In the Optional updates available area, you’ll find the link to download and install the update.
Microsoft Update Catalog	Yes	To get the standalone package for this update, go to the Microsoft Update Catalog website.
Windows Server Update Services (WSUS)	No	You can import this update into WSUS manually. See the Microsoft Update Catalog for instructions.

File information

For a list of the files that are provided in this update, download the file information for cumulative update 4566116.

Note Some files erroneously have “Not applicable” in the “File version” column of the CSV file. This might lead to false positives or false negatives when using some third-party scan detection tools to validate the build.

August 20, 2020—KB4566116 (OS Builds 18362.1049 and 18363.1049) Preview

Highlights

Improvements and fixes

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