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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

  • 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 temporarily can’t access correctly reissued certificates, 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 to 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 Server 2012, see the following article in the Microsoft Knowledge Base:

    4019110 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 Server 2012: 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 4019110 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've 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-RT-KB4014597-x64.msu

63391269977CFE619F133440DA182591E5A140C6

1EB39037E66DB71068AB0A546913BD2989F2B35C78FCA2B06FD25E9ADFAC89C7


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 x64-based systems

File name

File version

File size

Date

Time

msvcp120_clr0400.dll

12.0.52389.36389

678,592

29-Mar-2017

13:09

msvcr120_clr0400.dll

12.0.52389.36389

869,568

29-Mar-2017

13:09

penimc.dll

4.0.30319.36389

94,360

29-Mar-2017

13:09

presentationframework.dll

4.0.30319.36389

6,221,680

29-Mar-2017

13:09

presentationhost_v0400.dll

4.0.30319.36389

232,152

29-Mar-2017

13:09

presentationnative_v0400.dll

4.0.30319.36389

1,077,984

29-Mar-2017

13:09

system.core.dll

4.0.30319.36389

1,271,968

29-Mar-2017

13:09

system.security.dll

4.0.30319.36389

296,632

29-Mar-2017

13:09

system.windows.controls.ribbon.dll

4.0.30319.36389

751,512

29-Mar-2017

13:09

system.xaml.dll

4.0.30319.36389

640,672

29-Mar-2017

13:09

system.dll

4.0.30319.36389

3,487,872

28-Mar-2017

13:10

windowsbase.dll

4.0.30319.36389

1,241,928

29-Mar-2017

13:09

wpfgfx_v0400.dll

4.0.30319.36389

2,108,592

29-Mar-2017

13:09

presentationcore.dll

4.0.30319.36389

3,210,944

29-Mar-2017

13:09

presentationframework.dll

4.0.30319.36389

6,221,680

29-Mar-2017

13:09

system.core.dll

4.0.30319.36389

1,271,968

29-Mar-2017

13:09

system.security.dll

4.0.30319.36389

296,632

29-Mar-2017

13:09

system.windows.controls.ribbon.dll

4.0.30319.36389

751,512

29-Mar-2017

13:09

system.xaml.dll

4.0.30319.36389

640,672

29-Mar-2017

13:09

system.dll

4.0.30319.36389

3,487,872

28-Mar-2017

13:09

windowsbase.dll

4.0.30319.36389

1,241,928

29-Mar-2017

13:09

msvcp120_clr0400.dll

12.0.52389.36389

536,768

29-Mar-2017

13:09

msvcr120_clr0400.dll

12.0.52389.36389

875,712

29-Mar-2017

13:09

penimc.dll

4.0.30319.36389

81,048

29-Mar-2017

13:09

presentationhost_v0400.dll

4.0.30319.36389

186,080

29-Mar-2017

13:09

presentationnative_v0400.dll

4.0.30319.36389

790,248

29-Mar-2017

13:09

system.core.dll

4.0.30319.36389

1,271,968

29-Mar-2017

13:09

wpfgfx_v0400.dll

4.0.30319.36389

1,648,312

29-Mar-2017

13:09

presentationcore.dll

4.0.30319.36389

3,226,464

29-Mar-2017

13:09

 

How to obtain help and support for this security update

Applies to

This article applies to the following:
 

  • Microsoft .NET Framework 4.5.2 when used with:

    • Windows Server 2012

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