January 8, 2019—KB4480964 (Security-only update)

Applies to: Windows 8.1Windows Server 2012 R2

Improvements and fixes


This security update includes quality improvements. No new operating system features are being introduced in this update. Key changes include:

  • Provides protections against an additional subclass of speculative execution side-channel vulnerability known as Speculative Store Bypass (CVE-2018-3639) for AMD-based computers. These protections aren't enabled by default. For Windows client (IT pro) guidance, follow the instructions in KB4073119. For Windows Server guidance, follow the instructions in KB4072698. Use these guidance documents to enable mitigations for Speculative Store Bypass (CVE-2018-3639). Additionally, use the mitigations that have already been released for Spectre Variant 2 (CVE-2017-5715) and Meltdown (CVE-2017-5754).
  • Addresses an issue that affects PowerShell remoting loop back using non-administrator accounts. For more details, see Windows Security change affecting PowerShell

  • Security updates to Windows App Platform and Frameworks, Windows MSXML, Windows Kernel, Windows Storage and Filesystems, Windows Wireless Networking, and the Microsoft JET Database Engine.

For more information about the resolved security vulnerabilities, please refer to the Security Update Guide.

Known issues in this update


Microsoft is not currently aware of any issues with this update.

How to get this update


This update is now available for installation through WSUS. To get the stand-alone package for this update, go to the Microsoft Update Catalog website.

File information

For a list of the files that are provided in this update, download the file information for update 4480964