Table of contents
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Release Date:

09/03/2021

Version:

OS Build 14393.4283

NEW 3/9/21
IMPORTANT As part of the end of support for Adobe Flash, KB4577586 is now available as an optional update from Windows Update (WU) and Windows Server Update Services (WSUS). Installing KB4577586 will remove Adobe Flash Player permanently from your Windows device. Once installed, you cannot uninstall KB4577586. For more details about Microsoft’s plans, see Update on Adobe Flash Player End of Support.

11/19/20
For information about Windows update terminology, see the article about the types of Windows updates and the monthly quality update types. To view other notes and messages, see the Windows 10, version 1607 update history home page

Highlights

  • Updates security for the Windows user interface.

  • Updates to improve security when Windows performs basic operations.

  • Updates to improve security when using Microsoft Office products.

Improvements and fixes

This security update includes quality improvements. Key changes include:

  • Turns off token binding by default in Windows Internet (WinINet).

  • Addresses an issue in the Windows Management Instrumentation (WMI) service that causes a heap leak each time security settings are applied to WMI namespace permissions.

  • Addresses an issue in which a principal in a trusted MIT realm fails to obtain a Kerberos service ticket from Active Directory domain controllers (DC). This occurs on devices that installed Windows Updates that contain CVE-2020-17049 protections and configured PerfromTicketSignature to 1 or higher. These updates were released between November 10, 2020 and December 8, 2020. Ticket acquisition also fails with the error, “KRB_GENERIC_ERROR”, if callers submit a PAC-less Ticket Granting Ticket (TGT) as an evidence ticket without providing the USER_NO_AUTH_DATA_REQUIRED flag.

  • Addresses an elevation of privilege security vulnerability documented in CVE-2021-1640 related to print jobs submitted to “FILE:” ports. After installing Windows updates from March 9, 2021 and later, print jobs that are in a pending state before restarting the print spooler service or restarting the OS will remain in an error state. Manually delete the affected print jobs and resubmit them to the print queue when the print spooler service is online. 

  • Addresses a reliability issue in Remote Desktop.

  • Addresses an issue that might cause stop error 7E in nfssvr.sys on servers running the Network File System (NFS) service.

  • Addresses an issue that excessively logs DfsSvc Event 14554 in the System event log by default once every hour for each DFS Namespace (DFSN). This update adds a new registry key, RootShareAcquireSuccessEvent, to enable or disable Event 14554.

    Keypath: HKEY_LOCAL_MACHINE/L"System\CurrentControlSet\Services\Dfs\Parameters"

    Default value = 0

    If RootShareAcquireSuccessEvent is not 0 or is not present = Enable log.

    If RootShareAcquireSuccessEvent is 0 = Disable log.

    Whenever you change RootShareAcquireSuccessEvent, you must restart the DFSN service.

  • Addresses an issue that causes an increase in network traffic during update detection for Windows Updates. This issue occurs on devices that are configured to use an authenticated user proxy as the fallback method if update detection with a system proxy fails or there is no proxy.

  • Security updates to the Windows Shell, Windows User Account Control (UAC), Windows Fundamentals, Windows Core Networking, Windows Hybrid Cloud Networking, Windows Kernel, Windows Virtualization, the Microsoft Graphics Component, Internet Explorer, Microsoft Edge Legacy, and Windows Media.

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

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

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

After installing updates released March 9, 2021 or March 15, 2021, you might get unexpected results when printing from some apps. Issues might include:

  • Elements of the document might print as solid black/color boxes or might be missing, including barcodes, QR codes, and graphics elements, such as logos.

  • Table lines might be missing. Other alignment or formatting issues might also be present.

  • Printing from some apps or to some printers might result in a blank page or label.

This issue is resolved in KB5001633.

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 and applying Microsoft security fixes. 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 (KB5001078) 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 10

Classification: Security Updates

File information

For a list of the files that are provided in this update, download the file information for cumulative update 5000803

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