Description of the Security Only update for .NET Framework 3.5 for Windows 8.1 and Server 2012 R2 (KB 4483484)

Applies to: .NET


This security update resolves vulnerabilities in Microsoft .NET Framework that could allow the following:

  • A Remote Code Execution vulnerability in .NET Framework software if the software does not check the source markup of a file. An attacker who successfully exploits the vulnerability could run arbitrary code in the context of the current user. If the current user is logged on by using administrative user rights, an attacker could take control of the affected system. An 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 have administrative user rights.

    Exploitation of the vulnerability requires a user to open a specially crafted file that has an affected version of .NET Framework. In an email attack scenario, an attacker could exploit the vulnerability by sending the specially crafted file to the user and convincing the user to open the file.

    This security update addresses the vulnerability by correcting how .NET Framework checks the source markup of a file.

    To learn more about this vulnerability, see Microsoft Common Vulnerabilities and Exposures CVE-2019-0613.

  • A vulnerability in certain .NET Framework APIs that parse URLs. An attacker who successfully exploits this vulnerability could use it to bypass security logic that's intended to make sure that a user-provided URL belonged to a specific host name or a subdomain of that host name. This could be used to cause privileged communication to be made to an untrusted service as if it were a trusted service.

    To exploit the vulnerability, an attacker must provide a URL string to an application that tries to verify that the URL belongs to a specific host name or to a subdomain of that host name. The application must then make an HTTP request to the attacker-provided URL either directly or by sending a processed version of the attacker-provided URL to a web browser.

    To learn more about this vulnerability, see Microsoft Common Vulnerabilities and Exposures CVE-2019-0657.


  • All updates for Windows 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 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

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

4487123 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 4487123)

How to obtain and install the update

Method 1: Microsoft Update Catalog

To get the standalone 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. You must install the ActiveX control to continue.
  5. After the ActiveX control is installed, you see the Microsoft Update Catalog screen. Type 4487123 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 require, 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:

20190212 Security update deployment information: February 12, 2019

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 replaces updates 4481485 and 4457916.

Information about protection and security