SIGRed (CVE-2020-1350) is a mark for critical vulnerability of Windows Domain Name System server. It concerns all operating system Windows Server from version 2003 to 2019 on which the DNS service is active.
Microsoft has marked this vulnerability as the most critical (CVSS: 10.0) and from 14. July 2020 there is security patch available. If there is a Domain Name Server on your Windows system, either internal or external service, we would recommend to apply the patch as soon as possible.
Vulnerability does not concern Windows DNS client or other DNS servers.