Introducing the September 2021 Microsoft Windows security updates

Today is patch day at Microsoft, and the company has released security updates and non-security related updates for Windows and other company products. Security updates have been released for all client and server versions of the Windows operating system supported by Microsoft. Other company products, such as Microsoft Office, have also received updates.

Our preview of Windows security updates for September 2021 provides system administrators, IT professionals, and individuals with information on the updates released.

You can find the list of critical updates for each supported Windows operating system as well as the distribution of updates for each at the top. Below is information on released fixes, links to support pages, information on known issues, and download details.

Click here to open the August 2021 Windows Patch Day preview here.

Microsoft Windows security updates: September 2021

Click here to download an Excel spreadsheet listing all released security updates: Microsoft-windows-security-updates-list-september-2021

Abstract

• Microsoft has released security updates for all Windows client and server products.
• Security updates have been released for other company products such as Azure Sphere, Microsoft Edge, Microsoft Office, Visual Studio, Dynamics Business Central Control, or Microsoft Accessibility Insights for Android.
• The following client versions of Windows have known issues: Windows 7, Windows 8.1, Windows 10 version 1809, Windows 10 version 2004, 20H2 and 21H1
• The following server versions of Windows have known issues: Windows Server 2008, Windows Server 2008 R2, Windows Server 2012, Windows Server 2012 R2, Windows Server version 2004, and 20H2

Operating system distribution

• Windows 7 (extended support only): 22 vulnerabilities: 2 critical and 20 important
  • Windows Scripting Engine Memory Corruption Vulnerability – CVE-2021-26435
  • Windows WLAN AutoConfig Service Remote Code Execution Vulnerability – CVE-2021-36965
• Windows 8.1: 24 vulnerabilities: 2 critical and 22 important
• Windows 10 versions 1903 and 1909: 32 vulnerabilities: 2 critical and 30 important
• Windows 10 version 2004, 20H2 and 21H1: 32 vulnerabilities, 2 critical and 30 important

Windows Server Products

• Windows Server 2008 R2 (extended support only): 22 vulnerabilities: 2 critical and 20 important
  • Windows Scripting Engine Memory Corruption Vulnerability – CVE-2021-26435
  • Windows WLAN AutoConfig Service Remote Code Execution Vulnerability – CVE-2021-36965
• Windows Server 2012 R2: 24 vulnerabilities: 2 critical and 22 important
  • same as Windows Server 2008 R2.
• To windows server 2016: 28 vulnerabilities: 2 critical and 26 important
  • same as Windows Server 2008 R2.
• Windows Server 2019: 32 vulnerabilities: 2 critical and 30 important
  • same as Windows Server 2008 R2.
• Windows Server 2022: 29 vulnerabilities: 7 critical and 18 important
  • same as Windows Server 2008 R2.

Windows Security Updates

Windows 7 SP1 and Windows Server 2008 R2

Updates and Improvements:

• Addresses an issue in which a driver may not install if the driver is signed with multiple code signing signatures.
• This update also contains various security enhancements to internal operating system functionality.

Windows 8.1 and Windows Server 2012 R2

Updates and Improvements:

• This update contains various security enhancements to internal operating system functionality. No additional issues have been documented for this release.

Windows 10 version 1909

Updates and Improvements:

• Addresses an issue that causes PowerShell to create an infinite number of child directories. This problem occurs when you use the PowerShell Move-Item command to move a directory to one of its children. As a result, the volume fills up and the system stops responding.
• Security Updates

Windows 10 version 2004, 20H2 and 21H1

Updates and Improvements:

• Addresses an issue that causes PowerShell to create an infinite number of child directories. This problem occurs when you use the PowerShell Move-Item command to move a directory to one of its children. As a result, the volume fills up and the system stops responding.
• Security Updates

Other security updates

Cumulative Security Update 2021-09 for Internet Explorer (KB5005563)

Windows server

2021-09 Security Monthly Quality Rollup for Windows Server 2008 (KB5005606)

2021-09 Security Only Quality Update for Windows Server 2008 (KB5005618)

2021-09 Security Only Quality Update for Windows Embedded 8 Standard and Windows Server 2012 (KB5005607)

2021-09 Security Monthly Quality Rollup for Windows Embedded 8 Standard and Windows Server 2012 (KB5005623)

2021-09 Cumulative Update for Microsoft Server Operating System Version 21H2 for x64-based Systems (KB5005575)

2021-09 Cumulative Update for Windows Server 2016 and Windows 10 Version 1607 (KB5005573)

Maintaining Stack Updates

2021-09 Servicing Stack Update for Windows Server 2016 and Windows 10 Version 1607 (KB5005698)

Known issues

Windows 7 SP1 and Windows Server 2008 R2

• Some operations may fail on cluster shared volumes with the error “STATUS_BAD_IMPERSONATION_LEVEL (0xC00000A5)”
  • Workaround: Run the operations from an elevated process or from a node that does not have the CSV property
• Updates can be rolled back if the system does not support ESU.

Windows 8.1 and Windows Server 2012 R2

• Some operations may fail on cluster shared volumes with the error “STATUS_BAD_IMPERSONATION_LEVEL (0xC00000A5)”
  • Workaround: Run the operations from an elevated process or from a node that does not have the CSV property

Windows 10 version 1809

• Some devices with unspecified Asian language packs installed may generate the error “0x800f0982 – PSFX_E_MATCHING_COMPONENT_NOT_FOUND”.
  • Try uninstalling and reinstalling newly added language packs, then running a manual check for updates.
  • If that doesn’t work, Microsoft suggests using the Reset this PC feature and choosing to keep the files.

Windows 10 version 2004, 20H2 and 21H1

• Some devices may not be able to install the updates, which generates the error “PSFX_E_MATCHING_BINARY_MISSING”.
• Custom offline media or custom ISO image installations on devices can remove Microsoft Edge Legacy, but cannot replace it with Chromium-based Microsoft Edge.

Security advisories and updates

ADV 990001 – Latest Maintenance Stack Updates

Non-security updates

• 2021-09 Cumulative Update for .NET Framework 3.5 and 4.8 for Windows Server, Version 20H2, Windows 10 Version 20H2, Windows Server, Version 2004, Windows 10 Version 2004, Windows Server, Version 1909, Windows 10 Version 1909, Windows Server 2019 (1903) and Windows 10 version 1903 (KB5005548)

Microsoft Office Updates

You can find information about updating Office here.

How to download and install the September 2021 security updates

Security updates are downloaded and installed automatically through Windows Update on most home systems and some business / business systems.

Windows frequently checks for updates and automatically downloads those classified as security updates to install them.

Windows administrators can check for updates manually to download and install fixes immediately.

1. Select Start, type Windows Update, and load the Windows Update item that appears.
2. Select Check for Updates to run a manual check for updates.

Direct updates downloads

Below are resource pages with direct download links, if you prefer to download updates and install them manually.

Windows 7 and Server 2008 R2

• KB5005633 – 2021-09 Security Monthly Quality Rollup for Windows 7
• KB5005615 – 2021-09 Security Only Quality Update for Windows 7

Windows 8.1 and Windows Server 2012 R2

• KB5005613 – 2021-09 Security Monthly Quality Rollup for Windows 8.1
• KB5005627 – 2021-09 Security Only Quality Update for Windows 8.1

Windows 10 (version 1909)

• KB5005566 – 2021-09 cumulative update for Windows 10 Version 1909

Windows 10 (2004 version)

• KB5005565 – 2021-09 cumulative update for Windows 10 Version 2004

Windows 10 (version 20H2)

• KB5005565 – 2021-09 cumulative update for Windows 10 Version 20H2

Windows 10 (version 21H1)

• KB5005565 – 2021-09 cumulative update for Windows 10 Version 21H1

Additional resources

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