Security Only Update for .NET Framework 4.6, 4.6.1, 4.6.2, 4.7, 4.7.1, 4.7.2 for Windows 8.1 and Windows Server 2012 R2 (KB4578986)

Summary

An information disclosure vulnerability exists when the .NET Framework improperly handles objects in memory. An attacker who successfully exploited the vulnerability could disclose contents of an affected system's memory. To exploit the vulnerability, an authenticated attacker would need to run a specially crafted application. The update addresses the vulnerability by correcting how the .NET Framework handles objects in memory.

To learn more about the vulnerabilities, go to the following Common Vulnerabilities and Exposures (CVE).

CVE-2020-16937

Important

As a reminder to advanced IT administrators, updates to .NET Framework 3.5 for Windows 8.1 and Windows Server 2012 R2 should only be applied on systems where .NET Framework 3.5 is present and enabled. Customers who attempt to pre-install updates to .NET Framework 3.5 to offline images that do not contain the .NET Framework 3.5 product enabled will expose these systems to failures to enable .NET Framework 3.5 after the systems are online. For more extensive information about deploying .NET Framework 3.5, see Microsoft .NET Framework 3.5 Deployment Considerations.
All updates for Windows 8.1, Windows RT 8.1, and Windows Server 2012 R2 require that update KB 2919355 is installed. We recommend that you install update KB 2919355 on your Windows 8.1-based, Windows RT 8.1-based, or Windows Server 2012 R2-based computer so that you receive updates in the future.
If you install a language pack after you install this update, you must reinstall this update. Therefore, we recommend that you install any language packs that you need before you install this update. For more information, see Add language packs to Windows.

Additional information about this update

The following articles contain additional information about this update as it relates to individual product versions.

4580469 Description of the Security Only Update for .NET Framework 3.5, 4.5.2, 4.6, 4.6.1, 4.6.2, 4.7, 4.7.1, 4.7.2, 4.8 for Windows 8.1 and Windows Server 2012 R2 (KB4580469)

How to obtain and install the update

Before installing this update

Prerequisite:

To apply this update, you must have .NET Framework 4.6, 4.6.1, 4.6.2, 4.7, 4.7.1, 4.7.2 installed.

Install this update

Release Channel

Available

Next Step

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 and Windows Server 2012 R2

Classification: Security Updates

Prerequisites

To apply this update, you must have .NET Framework 4.6, 4.6.1, 4.6.2, 4.7, 4.7.1, 4.7.2 installed.

Restart requirement

You must restart the computer after you apply this update if any affected files are being used. We recommend that you exit all .NET Framework-based applications before you apply this update.

Update deployment information

For deployment details for this security update, go to the following article in the Microsoft Knowledge Base:

20201013 Security update deployment information: October 13, 2020

Update removal information

Note We do not recommend that you remove any security update. To remove this update, use the Programs and Features item in Control Panel.

Update restart information

This update does not require a system restart after you apply it unless files that are being updated are locked or are being used.

File information The English (United States) version of this software update installs files that have the attributes that are listed in the following tables.Windows 8.1, Windows RT 8.1 and Windows Server 2012 R2 file information

Note: The MANIFEST files (.manifest) and MUM files (.mum) that are installed are not listed.

File information

File hash information

File name	SHA1 hash	SHA256 hash
Windows8.1-KB4578986-x64.msu	A8943DA384E133995BE027390813F93A04942AEF	2814C50D6B28652F0331F54C96AEEE0307E8AB59F12CF18AACC327B7141E7A4F
Windows8.1-KB4578986-arm.msu	7B0A343F6A136E34B040E296FEE0E4BDED924084	B187213386FC4312DAB1490A27C6BE538D8BF1A296D742A01342B596E1AF5E2E
Windows8.1-KB4578986-x86.msu	486FE2BFA5DCFE06D0187551466A9E925B873AEF	046D7847A57408C64AAC935AFD1D34B5D28EF10D403F19FACEE0F54F621F17AF

For all supported x64-based versions

File name	File version	File size	Date	Time	Platform
System.security.dll	4.7.3700.0	318,728	28-Aug-2020	01:31	x86
System.security.dll	4.7.3700.0	318,728	28-Aug-2020	01:31	x86

For all supported ARM-based versions

File name	File version	File size	Date	Time	Platform
System.security.dll	4.7.3700.0	318,728	28-Aug-2020	01:31	x86

For all supported x86-based versions

File name	File version	File size	Date	Time	Platform
System.security.dll	4.7.3700.0	318,728	28-Aug-2020	01:31	x86

Information about protection and security

Protect yourself online: Windows Security support
Learn how we guard against cyber threats: Microsoft Security