Description of the Security Only update for .NET Framework 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 4457026)

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, RT 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:

Select Start, select Administrative Tools, and then select Microsoft Windows Server Update Services 3.0.
Expand ComputerName, and then select Action.
Select Import Updates.
WSUS opens a browser window in which you may be prompted to install an ActiveX control. Install the ActiveX control to continue.
After the ActiveX control is installed, you see the Microsoft Update Catalog screen. Type 4457915 in the Search box, and then select Search.
Locate the .NET Framework packages that match the operating systems, languages, and processors in your environment. Select Add to add them to your basket.
After you select all the packages that you need, select View Basket.
To import the packages to your WSUS server, select Import.
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-KB4457026-x86.msu	E196FFC353647C09C4E88D3DF1F29D5E57437D31	0B068C21B97BFC626EB974D5D232FB9B9DF007D04B455BC2358BD2838AB360C8
Windows8.1-KB4457026-x64.msu	718B5942BD69D2809C5BCCA96C2D2F384EF7864E	D75E3DBB8100A3F0296F5A7C6322BE1966280CC35F5A260F2DDBEC41491CA938

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	4.7.3180.0	1,054,216	07-Aug-2018	08:06
system.workflow.componentmodel.dll	4.7.3180.0	1,547,288	07-Aug-2018	08:06
system.workflow.runtime.dll	4.7.3180.0	501,752	07-Aug-2018	08:06
workflowservicehostperformancecounters.dll	4.7.3180.0	92,216	07-Aug-2018	08:06

File attributes for all supported x64-based systems