September 8, 2020—KB4577066 (Monthly Rollup)

IMPORTANT Windows 8.1 and Windows Server 2012 R2 have reached the end of mainstream support and are now in extended support. Starting in July 2020, there will no longer be optional, non-security releases (known as "C" releases) for this operating system. Operating systems in extended support have only cumulative monthly security updates (known as the "B" or Update Tuesday release).

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)”

Improvements and fixes

This security update includes improvements and fixes that were a part of update KB4571703 (released August 11, 2020) and addresses the following issues:

Updates time zone information for Yukon, Canada. For more information, see DST changes in Windows for Yukon, Canada: September 8, 2020.
Addresses an issue when you evaluate the compatibility status of the Windows ecosystem to help ensure application and device compatibility for all updates to Windows.
Addresses a security vulnerability issue with user proxies and HTTP-based intranet servers. After you install this update, HTTP-based intranet servers cannot leverage a user proxy to detect updates by default. Scans that use these servers will fail if the clients do not have a configured system proxy. If you must leverage a user proxy, you must configure the behavior by using the Windows Update policy “Allow user proxy to be used as a fallback if detection using system proxy fails.” This change does not affect customers who secure their Windows Server Update Services (WSUS) servers that use the Transport Layer Security (TLS) or Secure Sockets Layer (SSL) protocols. For more information, see Improving security for devices receiving updates via WSUS.
Security updates to Windows Media, Windows Input and Composition, Windows App Platform and Frameworks, Windows Graphics, Windows Cloud Infrastructure, Windows Authentication, Windows Cryptography, Windows Fundamentals, Windows Kernel, Windows Hybrid Cloud Networking, Windows Peripherals, Windows Storage and Filesystems, Windows Network Security and Containers, Windows Update Stack, the Microsoft Scripting Engine, and Windows SQL components.

For more information about the resolved security vulnerabilities, please refer to the Security Update Guide.

Known issues in this update

Symptom

Workaround

Certain operations, such as rename, that you perform on files or folders that are on a Cluster Shared Volume (CSV) may fail with the error, “STATUS_BAD_IMPERSONATION_LEVEL (0xC00000A5)”. This occurs when you perform the operation on a CSV owner node from a process that doesn’t have administrator privilege.

Do one of the following:

Perform the operation from a process that has administrator privilege.
Perform the operation from a node that doesn’t have CSV ownership.

Microsoft is working on a resolution and will provide an update in an upcoming release.

How to get this update

Before installing this update

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

If you use Windows Update, the latest SSU (KB4566425) 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 and Microsoft Update	Yes	None. This update will be downloaded and installed automatically from Windows 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)	Yes	This update will automatically sync with WSUS if you configure Products and Classifications as follows: Product: Windows 8.1, Windows Server 2012 R2, Windows Embedded 8.1 Industry Enterprise, Windows Embedded 8.1 Industry Pro Classification: Security Updates

File information

For a list of the files that are provided in this update, download the file information for update 4577066.

September 8, 2020—KB4577066 (Monthly Rollup)

Improvements and fixes

Known issues in this update

How to get this update

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