May 14, 2019—KB4499154 (OS Build 10240.18215)

Improvements and fixes

This update includes quality improvements. Key changes include:

• Provides protections against a new subclass of speculative execution side-channel vulnerabilities, known as Microarchitectural Data Sampling, for 64-Bit (x64) versions of Windows (CVE-2019-11091,CVE-2018-12126, CVE-2018-12127, CVE-2018-12130). Use the registry settings as described in the Windows Client article. (These registry settings are enabled by default for Windows Client OS editions).

• Adds "gov.uk" to the HTTP Strict Transport Security Top Level Domains (HSTS TLD) for Internet Explorer and Microsoft Edge.

• Addresses an issue that may cause “Error 1309” while installing or uninstalling certain types of .msi and .msp files on a virtual drive.

• Improves performance related to case-insensitive string comparison functions such as _stricmp() in the Universal C Runtime.

• Addresses an issue that prevents the Microsoft Visual Studio Simulator from starting.

• Addresses an issue that may cause the text, layout, or cell size to become narrower or wider than expected in Microsoft Excel when using the MS UI Gothic or MS PGothic fonts.

• Security updates to Internet Explorer, Microsoft Scripting Engine, Microsoft Edge, Windows Storage and Filesystems, Microsoft Graphics Component, Windows App Platform and Frameworks, Windows Cryptography, Windows Datacenter Networking, Windows Server, Windows Kernel, and the Microsoft JET Database Engine.

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, please refer to the Security Update Guide.

Known issues in this update

How to get this update

Before installing this update

Microsoft strongly recommends that you install the latest servicing stack update (SSU) for your operating system before installing the latest cumulative update (LCU). SSUs improve the reliability of the update process to mitigate potential issues while installing the LCU and applying Microsoft security fixes. For more information, see Servicing stack updates.

If you are using Windows Update, the latest SSU (KB4498353) will be offered to you automatically. To get the standalone package for the latest SSU, search for it in the Microsoft Update Catalog.

Install this update

This update will be downloaded and installed automatically from Windows Update. To get the standalone 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 cumulative update 4499154.