Affected: Microsoft Windows 10 Version 1703, Microsoft Windows 10 Version 1803, Microsoft Windows Server, version 1803 (Server Core Installation), Microsoft Windows 10 Version 1809, Microsoft Windows Server 2019, Microsoft Windows Server 2019 (Server Core installation), Microsoft Windows 10 Version 1709 for 32-bit Systems, Microsoft Windows 10 Version 1709, Microsoft Windows 10 Version 1903 for 32-bit Systems, Microsoft Windows 10 Version 1903 for x64-based Systems and 19 more

A tampering vulnerability exists in Microsoft Windows when a man-in-the-middle attacker is able to successfully bypass the NTLM MIC (Message Integrity Check) protection. An attacker who successfully exploited this vulnerability could gain the ability to downgrade NTLM security features. To exploit this vulnerability, the attacker would need to tamper with the NTLM exchange. The attacker could then modify flags of the NTLM packet without invalidating the signature. The update addresses the vulnerability by hardening NTLM MIC protection on the server-side.