January 12, 2021—KB4598285 (Monthly Rollup)

IMPORTANTAdobe Flash Player went out of support on December 31, 2020. For more information, see Adobe Flash end of support on December 31, 2020. Flash content will be blocked from running in Flash Player beginning January 12, 2021. For more information, see Adobe Flash Player EOL General Information Page.

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 improvements and fixes that were a part of update KB4592484 (released December 8, 2020) and addresses the following issues:

• Addresses a security bypass vulnerability that exists in the way the Printer Remote Procedure Call (RPC) binding handles authentication for the remote Winspool interface. For more information, see KB4599464.
• Addresses a security vulnerability issue with HTTPS-based intranet servers. After you install this update, HTTPS-based intranet servers cannot leverage a user proxy to detect updates by default. Scans that use these servers will fail if the clients do not have a configured system proxy.

If you must leverage a user proxy, you must configure the behavior by using the Windows Update policy Allow user proxy to be used as a fallback if detection using system proxy fails. To make sure that the highest levels of security, additionally leverage Windows Server Update Services (WSUS) Transport Layer Security (TLS) certificate pinning on all devices. For more information, see Changes to scans, improved security for Windows devices.

Note This change does not affect customers who use HTTP WSUS servers.

• Addresses an issue in which a principal in a trusted Managed Identity for Application (MIT) realm does not obtain a Kerberos Service ticket from Active Directory domain controllers (DCs). This issue occurs after Windows Updates that contains CVE-2020-17049 protections released between November 10 and December 8, 2020 are installed and PerfromTicketSignature is configured to1or higher. Ticket acquisition fails withKRB_GENERIC_ERRORif callers submit a PAC-less Ticket Granting Ticket (TGT) as an evidence ticket without providing theUSER_NO_AUTH_DATA_REQUIRED flag.
• Security updates to Windows App Platform and Frameworks, Windows Graphics, Windows Media, Windows Fundamentals, Windows Cryptography, and Windows Virtualization.
  For more information about the resolved security vulnerabilities, please refer to the new Security Update Guide website.

Known issues in this update

• 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.

How to get this update