January 12, 2021—KB4598243 (OS Build 14393.4169) - EXPIRED


None **NEW 8/5/21 EXPIRATION NOTICE****IMPORTANT **As of 8/5/2021, this KB is no longer available from Windows Update, the Microsoft Update Catalog, or other release channels. We recommend that you update your devices to the latest security quality update. **UPDATED 1/12/21 REMINDER **Adobe Flash Player went out of support on December 31, 2020. For more information, see [Adobe Flash end of support on December 31, 2020](<https://docs.microsoft.com/en-us/lifecycle/announcements/adobe-flash-end-of-support#:~:text=Adobe%20will%20end%20support%20of,site%2Dby%2Dsite%20basis.>). 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](<https://www.adobe.com/products/flashplayer/end-of-life.html>). **11/19/20** For information about Windows update terminology, see the article about the [types of Windows updates](<https://docs.microsoft.com/en-us/troubleshoot/windows-client/deployment/standard-terminology-software-updates>) and the [monthly quality update types](<https://techcommunity.microsoft.com/t5/windows-it-pro-blog/windows-10-update-servicing-cadence/ba-p/222376>). To view other notes and messages, see the Windows 10, version 1607 update history home page. ## Highlights * Updates to improve security when using Microsoft Office products. * Updates to improve security when using external devices, such as game controllers, printers, and web cameras. ## Improvements and fixes This security update includes quality improvements. Key changes include: * Adds the ability to set a Group Policy to show only the domain and username when a user signs in. * Addresses an issue that delays authentication traffic because of Netlogon scalability issues. * Addresses an issue in which a principal in a trusted MIT realm fails to obtain a Kerberos service ticket from Active Directory domain controllers (DC). This occurs on devices that installed Windows Updates that contain CVE-2020-17049 protections and configured PerfromTicketSignature to 1 or higher. These updates were released between November 10, 2020 and December 8, 2020. Ticket acquisition also fails with the error, “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. * 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 installing this update, HTTPS-based intranet servers cannot, by default, use a user proxy to detect updates. Scans using these servers will fail if you have not configured a system proxy on the clients. If you must use a user proxy, you must configure the behavior using the policy “Allow user proxy to be used as a fallback if detection using system proxy fails.” To ensure the highest levels of security, also use Windows Server Update Services (WSUS) Transport Layer Security (TLS) certificate pinning on all devices. This change does not affect customers who are using HTTP WSUS servers. For more information, see [Changes to scans, improved security for Windows devices](<https://aka.ms/WSUS-scans-part2>). * Addresses an issue in the Remote Desktop Protocol (RDP) redirector (**rdpdr.sys**) that causes a stop error. * Security updates to the Windows App Platform and Frameworks, Microsoft Graphics Component, Windows Media, Windows Fundamentals, Windows Cryptography, Windows Virtualization, Windows Peripherals, and Windows Hybrid Storage Services. 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 new [Security Update Guide](<https://msrc.microsoft.com/update-guide>) website. **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** ---|--- After installing KB4467684, the cluster service may fail to start with the error “2245 (NERR_PasswordTooShort)” if the group policy “Minimum Password Length” is configured with greater than 14 characters.| This issue is resolved in KB4601318. ## 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 general information about SSUs, see [Servicing stack updates](<https://docs.microsoft.com/en-us/windows/deployment/update/servicing-stack-updates>) and Servicing Stack Updates (SSU): Frequently Asked Questions.If you are using Windows Update, the latest SSU (KB4576750) will be offered to you automatically. To get the standalone package for the latest SSU, search for it in the [Microsoft Update Catalog](<http://www.catalog.update.microsoft.com/home.aspx>). **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](<https://www.catalog.update.microsoft.com/Search.aspx?q=KB4598243>) website. Windows Server Update Services (WSUS)| Yes| This update will automatically sync with WSUS if you configure **Products and Classifications** as follows:**Product**: Windows 10**Classification**: Security Updates **File information**For a list of the files that are provided in this update, download the [file information for cumulative update 4598243](<https://download.microsoft.com/download/a/9/c/a9cc5807-bbe4-4aad-bb18-14455a62ae38/4598243.csv>).