This also applies to:

  • Microsoft .NET Framework 3.5

Summary

This security update resolves a vulnerability in Microsoft .NET Framework that could allow remote code execution when .NET Framework processes untrusted input. An attacker who successfully exploits this vulnerability in software by using .NET Framework could take control of an affected system. The attacker could then install programs; view, change, or delete data; or create new accounts that have full user rights. Users whose accounts are configured to have fewer user rights on the system could be less affected than users who operate with administrative user rights.

To exploit the vulnerability, an attacker would first have to convince the user to open a malicious document or application.

This security update addresses the vulnerability by correcting how .NET Framework validates untrusted input.

To learn more about this vulnerability, see Microsoft Common Vulnerabilities and Exposures CVE-2018-8421.

Important

  • 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 security update

For more information about this security update as it relates to Windows 8.1, Windows RT 8.1, and Windows Server 2012 R2, see the following article in the Microsoft Knowledge Base:

4457916 Security Only updates for .NET Framework 3.5, 4.5.2, 4.6, 4.6.1, 4.6.2, 4.7, 4.7.1, and 4.7.2 for Windows 8.1 and Server 2012 R2 (KB 4457916)

Known issues

After the September 2018 .NET Framework security update is applied to resolve CVE-2018-8421 (.NET Framework remote code execution vulnerability), SharePoint out-of-the-box workflows stop working.

For more information about this known issue, see the following article in the Microsoft Knowledge Base:

4465015 SharePoint Workflows stop working after you install .NET security updates for CVE-2018-8421

How to obtain and install the update

Method 1: Microsoft Update Catalog

To get the stand-alone package for this update, go to the Microsoft Update Catalog.

Method 2: Windows Software Update Services (WSUS)

On your WSUS server, follow these steps:

  1. Select Start, select Administrative Tools, and then select Microsoft Windows Server Update Services 3.0.

  2. Expand ComputerName, and then select Action.

  3. Select Import Updates.

  4. WSUS opens a browser window in which you may be prompted to install an ActiveX control. Install the ActiveX control to continue.

  5. After the ActiveX control is installed, you see the Microsoft Update Catalog screen. Type 4457915 in the Search box, and then select Search.

  6. Locate the .NET Framework packages that match the operating systems, languages, and processors in your environment. Select Add to add them to your basket.

  7. After you select all the packages that you need, select View Basket.

  8. To import the packages to your WSUS server, select Import.

  9. After the packages are imported, select Close to return to WSUS.

The updates are now available for installation through WSUS.

Update deployment information

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

20180911 Security update deployment information: September 11, 2018

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.

Update replacement information

This update does not replace any previously released update.

File information

File hash

File name

SHA1 hash

SHA256 hash

Windows8.1-KB4457056-x86.msu

04ABBCC751DAE38C8A5E67A98B20CD44425D9364

832C49EE9F17AAAE8D4F8D728B1FFF6B37D9365CB32D3DB22F202FB4EE696A0A

Windows8.1-KB4457056-x64.msu

B8840809D4890369CC0002B95EBCD6746466CB7B

D280196000A0CE3416CD4156E6345E1EADB28D9D062367EDDB48403F006F249C


File attributes for all supported x86-based systems

The English (United States) version of this update installs files that have the attributes that are listed in the following tables. The dates and times for these files are listed in Coordinated Universal Time (UTC). The dates and times for these files on your local computer are displayed in your local time together with your current daylight saving time (DST) bias. Additionally, the dates and times may change when you perform certain operations on the files.

File name

File version

File size

Date

Time

system.workflow.activities.dll

3.0.4203.8811

1,142,784

10-Aug-2018

13:11

system.workflow.componentmodel.dll

3.0.4203.8811

1,630,208

10-Aug-2018

13:11

system.workflow.runtime.dll

3.0.4203.8811

540,672

10-Aug-2018

13:11

system.workflow.activities.dll

3.0.4203.8811

1,142,784

10-Aug-2018

13:11

system.workflow.componentmodel.dll

3.0.4203.8811

1,630,208

10-Aug-2018

13:11

system.workflow.runtime.dll

3.0.4203.8811

540,672

10-Aug-2018

13:11

File attributes for all supported x64-based systems

The English (United States) version of this update installs files that have the attributes that are listed in the following tables. The dates and times for these files are listed in Coordinated Universal Time (UTC). The dates and times for these files on your local computer are displayed in your local time together with your current daylight saving time (DST) bias. Additionally, the dates and times may change when you perform certain operations on the files.

File name

File version

File size

Date

Time

system.workflow.activities.dll

3.0.4203.8811

1,060,864

10-Aug-2018

13:11

system.workflow.componentmodel.dll

3.0.4203.8811

1,519,616

10-Aug-2018

13:11

system.workflow.runtime.dll

3.0.4203.8811

454,656

10-Aug-2018

13:11

system.workflow.activities.dll

3.0.4203.8811

1,142,784

10-Aug-2018

13:11

system.workflow.componentmodel.dll

3.0.4203.8811

1,630,208

10-Aug-2018

13:11

system.workflow.runtime.dll

3.0.4203.8811

540,672

10-Aug-2018

13:11

system.workflow.activities.dll

3.0.4203.8811

1,142,784

10-Aug-2018

13:11

system.workflow.componentmodel.dll

3.0.4203.8811

1,630,208

10-Aug-2018

13:11

system.workflow.runtime.dll

3.0.4203.8811

540,672

10-Aug-2018

13:11

How to obtain help and support for this security update

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