March 22, 2018—KB4088891 (OS Build 15063.994)


Improvements and fixes


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

  • Addresses issue with a GDI handle leak in the Windows Ribbon control.

  • Addresses issue where, during BitLocker decryption or encryption of a drive, files protected with the Encrypting File System (EFS) may become corrupted.

  • Addresses issue where, when an iSCSI request contains an incomplete header in the first packet, iSCSI may not recognize when a request has been sent.

  • Adds support in stornvme for additional SSDs.

  • Addresses issue where the Japanese keyboard layout was not functioning properly during a Remote Assistance session.
  • Addresses rendering issue in Microsoft Edge for PDF documents with backgrounds created using various third-party publishing tools. 
  • Addresses issue that decreases the Universal CRT’s performance in the _gcvt and _gcvt_s functions.
  • Addresses issue in which the output to a file or pipe was fully buffered in the Universal CRT for the standard error (STDERR) stream.
  • Addresses issue in the Universal CRT by adding the "x" access mode flag to support the fopen() function.
  • Addresses issue with a race condition in the Universal C Runtime (CRT) that occurs when you update the global locale. The issue corrupts the current locale reference count and triggers a double free condition.

If you installed earlier updates, only the new fixes contained in this package will be downloaded and installed on your device.

For more information about the resolved security vulnerabilities, see 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 will be downloaded and installed if you go to the Windows Settings > Update & Security > Windows Update page, and click Check online for updates from Microsoft Update.

To get the standalone package for this update, go to the Microsoft Update Catalog website.

Important When installing both the servicing stack update (SSU) (KB4088825) and the latest cumulative update (LCU) from the Microsoft Update Catalog, install the SSU before installing the LCU.

File information

For a list of the files that are provided in this update, download the file information for cumulative update 4088891