Microsoft has released several urgent updates to Windows 10, without waiting for scheduled updates on schedule. First there was an update KB4594442 for Windows 10 version 1809 (released in November 2018), and then became available KB4594443 for Windows 10 versions 1903 and 1909, as well as KB4594440 for the OS version 2020 – under the numbers 2004 and 20H2. Moreover, they did not forget even the long-outdated 1607 – “Jubilee Update”, which was released on August 2, 2016.
All of these updates are designed to address a serious authentication issue that many have encountered since installing the recent security patch. Vulnerability CVE-2020-17049 was present in the Kerberos authentication protocol and with a scheduled November update, Microsoft tried to close it, but “something went wrong.” As noted by Microsoft itself, the problem with Kerberos authentication arose due to bugs in the patch, fixing CVE-2020-17049 and released as part of the November “Tuesday updates”.