Microsoft CVE-2019-0820: .NET Framework and .NET Core Denial of Service Vulnerability

A denial of service vulnerability exists when .NET Framework and .NET Core improperly process RegEx strings. An attacker who successfully exploited this vulnerability could cause a denial of service against a .NET application.
A remote unauthenticated attacker could exploit this vulnerability by issuing specially crafted requests to a .NET Framework (or .NET core) application.
The update addresses the vulnerability by correcting how .NET Framework and .NET Core applications handle RegEx string processing.