January 12, 2021—KB4598278 (Monthly Rollup)

Improvements and fixes

This security update includes improvements and fixes that were a part of update KB4592468 (released previous 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 to 1 or higher. Ticket acquisition fails with KRB_GENERIC_ERROR if callers submit a PAC-less Ticket Granting Ticket (TGT) as an evidence ticket without providing the USER_NO_AUTH_DATA_REQUIRED flag.

• Security updates to Windows App Platform and Frameworks, Windows Graphics, Windows Media, Windows Fundamentals, Windows Cryptography, Windows Virtualization, and Windows Hybrid Storage Services.

For more information about the resolved security vulnerabilities, please refer to the new Security Update Guide website.

Known issues in this update

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 installing 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 (KB4566426) 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

File information

For a list of the files that are provided in this update, download the file information for update 4598278.