Description of the security update for the .NET Framework 4.5.1 and the .NET Framework 4.5.2 on Windows 8.1, Windows RT 8.1, and Windows Server 2012 R2: May 13, 2014


This update is for the Microsoft .NET Framework to disable RC4 in Transport Layer Security (TLS) through the modification of the system registry. Use of RC4 in TLS could allow an attacker to perform man-in-the-middle attacks and recover plaintext from encrypted sessions.


Microsoft has released a security advisory about this issue for IT professionals. The security advisory contains additional security-related information. To view the security advisory, go to the following Microsoft website:

More information about this security update

Download information

This update is available for download from the Microsoft Download Center.

Command-line switches for this update

Learn about the various command-line switches that are supported by this Microsoft .NET Framework update.

Restart information

This update does not require a system restart after you apply it unless the files that are being updated are locked or being used.

Update replacement information

This update does not replace any previously released update.

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.

Applies to

This article applies to the following:
  • Microsoft .NET Framework 4.5.1 when used with:
    • Windows 8.1
    • Windows RT 8.1
    • Windows Server 2012 R2
  • Microsoft .NET Framework 4.5.2 when used with:
    • Windows 8.1
    • Windows RT 8.1
    • Windows Server 2012 R2