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)

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Summary

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.

Important

• All updates for Windows 8.1 and Windows Server 2012 R2 require that update 2919355 is installed. We recommend that you install update 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

The following articles contain additional information about this update as it relates to individual product versions.

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

• 4483472 Description of the Security Only update for .NET Framework 4.5.2 for Windows 8.1 and Server 2012 R2 (KB 4483472)

• 4483469 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 4483469)