April 13, 2021 - KB5001393 (Security-only update)
Important: Windows 8.1 and Windows Server 2012 R2 have reached the end of mainstream support and are now in extended support. Starting in July 2020, there will no longer be optional, non-security releases (known as "C" releases) for this operating system. Operating systems in extended support have only cumulative monthly security updates (known as the "B" or Update Tuesday release).
For information about the various types of Windows updates, such as critical, security, driver, service packs, and so on, please see the following article. To view other notes and messages, see the Windows 8.1 and Windows Server 2012 R2 update history home page.
Improvements and fixes
This security update includes quality improvements. Key changes include:
For more information about the resolved security vulnerabilities, please refer to the new Security Update Guide website.
- Addresses a time zone change for Volgograd, Russia from UTC+4 to UTC+3 Moscow Standard Time (MSK).
- Addresses a time zone change for The Republic of South Sudan from UTC+3 to UTC+2 Juba. For more information about this change, see KB 4601275.
- Security updates to Windows Input and Composition, Windows Fundamentals, Windows Hybrid Cloud Networking, Windows Kernel, and Windows Media.
Known issues in this update
Symptom Workaround Certain operations, such as rename, that you perform on files or folders that are on a Cluster Shared Volume (CSV) may fail with the error, “STATUS_BAD_IMPERSONATION_LEVEL (0xC00000A5)”. This occurs when you perform the operation on a CSV owner node from a process that doesn’t have administrator privilege. Do one of the following:
Microsoft is working on a resolution and will provide an update in an upcoming release.
- Perform the operation from a process that has administrator privilege.
- Perform the operation from a node that doesn’t have CSV ownership.
How to get this update
Before installing this update
We strongly recommend that you install the latest servicing stack update (SSU) for your operating system before you install the latest Rollup. SSUs improve the reliability of the update process to mitigate potential issues while installing the Rollup and applying Microsoft security fixes. For general information about SSUs, see Servicing stack updates and Servicing Stack Updates (SSU): Frequently Asked Questions.
If you use Windows Update, the latest SSU (KB5001403) will be offered to you automatically. To get the standalone package for the latest SSU, search for it in the Microsoft Update Catalog.
REMINDER If you are using Security-only updates, you will also need to install all previous Security-only updates and the latest cumulative update for Internet Explorer (KB5000800).
Install this update
Release Channel Available Next Step Windows Update and Microsoft Update No See the other options below. Microsoft Update Catalog Yes To get the standalone package for this update, go to the Microsoft Update Catalog website. Windows Server Update Services (WSUS) Yes This update will automatically sync with WSUS if you configure Products and Classifications as follows:
Product: Windows 8.1, Windows Server 2012 R2, Windows Embedded 8.1 Industry Enterprise, Windows Embedded 8.1 Industry Pro
Classification: Security Updates
For a list of the files that are provided in this update, download the file information for update 5001393.
Source: April 13, 2021—KB5001393 (Security-only update)
Direct download links for KB5001393 MSU file from Microsoft Update Catalog:
Download KB5001393 MSU for Windows 8.1 32-bit (x86) - 29.8 MB
Download KB5001393 MSU for Windows 8.1 64-bit (x64) - 53.6 MB