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Summary

This security update for the Microsoft .NET Framework resolves a security feature bypass vulnerability in which the .NET Framework (and the .NET Core) components don't completely validate certificates. To learn more about this vulnerability, see Microsoft Common Vulnerabilities and Exposures CVE-2017-0248.

This update also contains security-enhancing fixes to the Windows Presentation Framework PackageDigitalSignatureManager component's ability to sign packages with the SHA256 hash algorithm.

Important

  • All future security and nonsecurity updates for Windows RT 8.1, Windows 8.1, and Windows Server 2012 R2 require update 2919355 to be installed. We recommend that you install update 2919355 on your Windows RT 8.1-based, Windows 8.1-based, or Windows Server 2012 R2-based computer so that you receive future updates.

  • 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

Serious problems might occur if you modify the registry incorrectly by using Registry Editor or by using another method. These problems might require that you reinstall the operating system. Microsoft cannot guarantee that these problems can be solved. Modify the registry at your own risk.

  • Enhanced Key Usage (EKU) is described in RFC 5280 in section 4.2.1.12: This extension indicates one or more purposes for which the certified public key may be used, in addition to or in place of the basic purposes that are indicated in the key usage extension. For example, a certificate that’s used for the authentication of a client to a server must be configured for Client Authentication. Similarly, a certificate that’s used for the authentication of a server must be configured for Server Authentication.

    When certificates are used for authentication, the authenticator examines the client certificate and seeks the correct purpose object identifier in Application Policies extensions. For example, the object identifier for Client Authentication is 1.3.6.1.5.5.7.3.2. When a certificate is used for client authentication, this object identifier must be present in the EKU extensions of the certificate or authentication fails. Certificates that have no EKU extension continue to authenticate correctly.

    If you can’t access correctly reissued certificates temporarily, you can choose to opt in or out of the security change across all computer operations to avoid any connectivity effects. To do this, specify the following registry key settings, depending on which .NET Framework version your application is targeting.

    Method 1: Updating registry key (available for all versions)

    Note This registry entry must be a DWORD entry.

    • For 32-bit process on 32-bit system and 64-bit process on 64-bit system:

      HKEY_LOCAL_MACHINE\Software\Microsoft\.NETFramework\v4.0.30319@RequireCertificateEKUs=0

    • For 32-bit process on 64-bit system:

      HKEY_LOCAL_MACHINE \Software\Wow6432Node\Microsoft\.NETFramework\v4.0.30319@RequireCertificateEKUs=0

    You can also opt out on a per-application basis. The following options are available for disabling this change to make sure that application compatibility is maintained.

    Method 2: Disable the policy for individual applications

    Note This registry entry must be a DWORD entry. The only valid value is 0. Any other value is ignored.

    • For 32-bit process on 32-bit system and 64-bit process on 64-bit system:

      HKEY_LOCAL_MACHINE\Software\Microsoft\.NETFramework\v4.0.30319@System.Net.ServicePointManager.RequireCertificateEKUs
      S:\Prj\console_pg\console_pg45\bin\Release\console_pg45.exe=0
      C:\MyApp\MyApp.exe=0

    • For 32-bit process on 64-bit system:

      HKEY_LOCAL_MACHINE \Software\Wow6432Node\Microsoft\.NETFramework\v4.0.30319@System.Net.ServicePointManager.RequireCertificateEKUs
      S:\Prj\console_pg\console_pg45\bin\Release\console_pg45.exe=0
      C:\MyApp\MyApp.exe=0

    Method 3: Using configuration API (available for the .NET Framework 4.6 and later versions)

    Starting in the .NET Framework 4.6, you can change the configuration at an application level through code, an application configuration, or registry changes.

    Configuring the switch in the .NET Framework 4.6

    Note The following examples disable the security feature.

    • Programmatically

      The first thing that the application should do is run the following code. This is because Service Point Manager initializes only one time.
        private const string DisableCachingName = @"TestSwitch.LocalAppContext.DisableCaching"; private const string DontCheckCertificateEKUsName= @"Switch.System.Net.DontCheckCertificateEKUs"; AppContext.SetSwitch(DisableCachingName, true); AppContext.SetSwitch(DontCheckCertificateEKUsName, true);

    • Application configuration

      To change the application configuration, add the following entry:
        <runtime> <AppContextSwitchOverrides value="Switch.System.Net.DontCheckCertificateEKUsName=true"/> </runtime>

    • Registry key (machine global):

      Registry location: HKEY_LOCAL_MACHINE\Software\[Wow6432Node\]Microsoft\.NETFramework\AppContext\Switch.System.Net.DontCheckCertificateEKUsName

      Type: String
      Value: "true"

    Note By default, Switch.System.Net.DontCheckCertificateEKUsName = True for all .NET Framework 4.x applications that are running on the .NET Framework 4.6 and later versions.

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

    4019111 Security Only update for the .NET Framework 3.5 Service Pack 1, 4.5.2, 4.6, 4.6.1, and 4.6.2 updates for Windows 8.1 and Windows Server 2012 R2: May 9, 2017

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. Click Start, click Administrative Tools, and then click Microsoft Windows Server Update Services 3.0.

  2. Expand ComputerName, and then click Action.

  3. Click Import Updates.

  4. WSUS will open a browser window in which you may be prompted to install an ActiveX control. You must install the ActiveX control to continue.

  5. Once the control is installed, you will see the Microsoft Update Catalog screen. Enter 4019111 in the Search box, and then click Search.

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

  7. When you have selected all the packages you need, click View Basket.

  8. Click Import to import the packages to your WSUS server.

  9. Click Close once the packages have been imported 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:

20170509 Security update deployment information: May 9, 2017

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

Package Name

Package Hash SHA 1

Package Hash SHA 2

Windows8.1-KB4014587-x64.msu

D3837DC9058590E610A8FF83D4707FD3576588B2

2B7D9615FE505F323BA5C997CDF0BD01B7D6CA11B31A07A393FFDD831CACE9E3

Windows8.1-KB4014587-x86.msu

98EB8EC2B0B2E00E1EEC17388AED45E3B2FD3600

FF1C7C43DCFF4979FB336311DFA06FD185ADFFB0461EF8263CB4649BDE5F76B0


The English (United States) version of this hotfix installs files that have the attributes that are listed in the following tables. The dates and the times for these files are listed in Coordinated Universal Time (UTC). The dates and the 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 the times may change when you perform certain operations on the files.

For all x86-based systems

File name

File version

File size

Date

Time

presentationframework.dll

4.6.1647.0

6,190,960

27-Mar-2017

04:08

system.core.dll

4.6.1647.0

1,349,280

27-Mar-2017

04:08

system.windows.controls.ribbon.dll

4.6.1647.0

742,808

27-Mar-2017

04:08

system.xaml.dll

4.6.1647.0

631,456

27-Mar-2017

04:08

system.dll

4.6.1647.0

3,506,824

27-Mar-2017

04:08

windowsbase.dll

4.6.1647.0

1,277,768

27-Mar-2017

04:08

msvcp120_clr0400.dll

12.0.52512.0

484,552

20-Mar-2017

05:16

msvcr120_clr0400.dll

12.0.52512.0

987,848

20-Mar-2017

05:16

penimc.dll

4.6.1647.0

81,560

27-Mar-2017

04:08

presentationhost_v0400.dll

4.6.1647.0

197,848

27-Mar-2017

04:08

presentationnative_v0400.dll

4.6.1647.0

826,592

27-Mar-2017

04:08

system.core.dll

4.6.1647.0

1,349,280

27-Mar-2017

04:08

wpfgfx_v0400.dll

4.6.1647.0

1,759,920

27-Mar-2017

04:08

presentationcore.dll

4.6.1647.0

3,521,880

27-Mar-2017

04:08

For all x64-based systems

File name

File version

File size

Date

Time

msvcp120_clr0400.dll

12.0.52512.0

690,016

20-Mar-2017

05:16

msvcr120_clr0400.dll

12.0.52512.0

993,632

20-Mar-2017

05:16

penimc.dll

4.6.1647.0

97,432

27-Mar-2017

04:01

presentationframework.dll

4.6.1647.0

6,190,960

27-Mar-2017

04:08

presentationhost_v0400.dll

4.6.1647.0

254,680

27-Mar-2017

04:01

presentationnative_v0400.dll

4.6.1647.0

1,107,680

27-Mar-2017

04:01

system.core.dll

4.6.1647.0

1,349,280

27-Mar-2017

04:08

system.windows.controls.ribbon.dll

4.6.1647.0

742,808

27-Mar-2017

04:08

system.xaml.dll

4.6.1647.0

631,456

27-Mar-2017

04:08

system.dll

4.6.1647.0

3,506,824

27-Mar-2017

04:08

windowsbase.dll

4.6.1647.0

1,277,768

27-Mar-2017

04:08

wpfgfx_v0400.dll

4.6.1647.0

2,262,712

27-Mar-2017

04:01

presentationcore.dll

4.6.1647.0

3,504,320

27-Mar-2017

04:01

presentationframework.dll

4.6.1647.0

6,190,960

27-Mar-2017

04:08

system.core.dll

4.6.1647.0

1,349,280

27-Mar-2017

04:08

system.windows.controls.ribbon.dll

4.6.1647.0

742,808

27-Mar-2017

04:08

system.xaml.dll

4.6.1647.0

631,456

27-Mar-2017

04:08

system.dll

4.6.1647.0

3,506,824

27-Mar-2017

04:08

windowsbase.dll

4.6.1647.0

1,277,768

27-Mar-2017

04:08

msvcp120_clr0400.dll

12.0.52512.0

484,552

20-Mar-2017

05:16

msvcr120_clr0400.dll

12.0.52512.0

987,848

20-Mar-2017

05:16

penimc.dll

4.6.1647.0

81,560

27-Mar-2017

04:08

presentationhost_v0400.dll

4.6.1647.0

197,848

27-Mar-2017

04:08

presentationnative_v0400.dll

4.6.1647.0

826,592

27-Mar-2017

04:08

system.core.dll

4.6.1647.0

1,349,280

27-Mar-2017

04:08

wpfgfx_v0400.dll

4.6.1647.0

1,759,920

27-Mar-2017

04:08

presentationcore.dll

4.6.1647.0

3,521,880

27-Mar-2017

04:08

 

How to obtain help and support for this security update

Applies to

This article applies to the following:
 

  • Microsoft .NET Framework 4.6.2 when used with:

    • Windows Server 2012 R2

    • Windows 8.1

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