Applies to:

Microsoft .NET Framework 3.5

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).

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 3.5 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 3.5 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 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-KB4578981-x64.msu

AF6AF9EE52CBA26F7A2604CBED0E50A23ACF0318

ED6D598F745BF1E235F5DDF959F667CDC2718542AB9274435B6BFB4AD8755A67

Windows8.1-KB4578981-x86.msu

3860CEBFB974C2020C39E919ACF73035764CADC0

577686098ACFA888835D2F4A7704423EB7B52558F67B415FAEFCFDFD4A303D39

For all supported x64-based versions

File name

File version

File size

Date

Time

Platform

System.security.dll

2.0.50727.8952

274,432

29-Aug-2020

13:35

x86

System.security.dll

2.0.50727.8952

274,432

29-Aug-2020

13:32

x86

For all supported x86-based versions

File name

File version

File size

Date

Time

Platform

System.security.dll

2.0.50727.8952

274,432

29-Aug-2020

13:32

x86

Information about protection and security

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