October 8, 2019—KB4520010 (OS Build 15063.2108)

IMPORTANT Windows 10 Enterprise and Windows 10 Education editions reached end of service on October 8, 2019. To continue receiving security and quality updates, Microsoft recommends updating to the latest version of Windows 10 .

Reminder March 12 and April 9 were the last two Delta updates for Windows 10, version 1703. Security and quality updates will continue to be available via the express and full cumulative update packages. For more information on this change please visit our blog.

Windows 10, version 1703, reached end of service on October 8, 2018 . Devices running Windows 10 Home, Pro, Pro for Workstation, and IoT Core editions will no longer receive monthly security and quality updates that contain protection from the latest security threats. To continue receiving security and quality updates, Microsoft recommends updating to the latest version of Windows 10.

Windows 10 Mobile, version 1703, reached end of service on June 11, 2019. Devices running Windows 10 Mobile and Windows 10 Mobile Enterprise will no longer receive monthly security and quality updates that contain protection from the latest security threats. To continue receiving security and quality updates, Microsoft recommends updating to the latest version of Windows 10.

ePub support ending in Microsoft Edge Microsoft Edge will end support for e-books that use the .epub file extension over the next several months. For more information, see Download an ePub app to keep reading e-books.

For more information about the various types of Windows updates, such as critical, security, driver, service packs, and so on, please see the following article.

Highlights

• Updates to improve security when using Internet Explorer and Microsoft Edge.
• Updates for verifying user names and passwords.
• Updates for storing and managing files.

Improvements and fixes

This security update includes quality improvements. Key changes include:

• Addresses an issue in security bulletin CVE-2019-1318 that may cause client or server computers that don’t support Extended Master Secret (EMS) RFC 7627 to have increased connection latency and CPU utilization. This issue occurs while performing full Transport Layer Security (TLS) handshakes from devices that don’t support EMS, especially on servers. EMS support has been available for all the supported versions of Windows since calendar year 2015 and is being incrementally enforced by the installation of the October 8, 2019 and later monthly updates.
• Addresses an issue with applications and printer drivers that utilize the Windows JavaScript engine (jscript.dll) for processing print jobs.
• Security updates to Microsoft Edge, Internet Explorer, Windows App Platform and Frameworks, Windows Cryptography, Windows Authentication, Windows Datacenter Networking, Windows Storage and Filesystems, Microsoft JET Database Engine, Windows Kernel, Microsoft Scripting Engine, and Windows Server .

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.

Windows Update Improvements Microsoft has released an update directly to the Windows Update client to improve reliability. Any device running Windows 10 configured to receive updates automatically from Windows Update, including Enterprise and Pro editions, will be offered the latest Windows 10 feature update based on device compatibility and Windows Update for Business deferral policy. This doesn’t apply to long-term servicing editions.

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:

• Perform the operation from a process that has administrator privilege.
• Perform the operation from a node that doesn’t have CSV ownership.

Microsoft is working on a resolution and will provide an update in an upcoming release.
Updates for Windows released October 8, 2019 or later provide protections, tracked by CVE-2019-1318, against an attack that could allow unauthorized access to information or data within TLS connections. This type of attack is known as a man-in-the-middle exploit. Windows might fail to connect to TLS clients and servers that do not support Extended Master Secret for resumption (RFC 7627). Lack of RFC support might cause one or more of the following errors or logged events:

• “The request was aborted: Could not create SSL/TLS secure Channel”

• SCHANNEL event 36887 is logged in the System event log with the description, “A fatal alert was received from the remote endpoint. The TLS protocol defined fatal alert code is 20.​”

| For information, see KB4528489.

How to get this update

Before installing this update Microsoft strongly recommends 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 (KB4521859) 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****Release Channel	Available	Next Step
Windows Update and Microsoft Update	Yes	None. This update will be downloaded and installed automatically from Windows Update.
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 synchronize with WSUS if you configure Products and Classifications as follows:Product : Windows 10Classification : Security Updates File information For a list of the files that are provided in this update, download the file information for cumulative update 4520010.