An information disclosure vulnerability exists in RPC if the server has Routing and Remote Access enabled. An attacker who successfully exploited this vulnerability could obtain information to further compromise the user’s system To exploit this vulnerability, an attacker would need to run a specially crafted application against an RPC server which has Routing and Remote Access enabled. Routing and Remote Access is a non-default configuration; systems without it enabled are not vulnerable. The security update addresses the vulnerability by correcting how the Routing and Remote Access service handles requests.
https://www.tenable.com/blog/microsoft-s-august-2020-patch-tuesday-addresses-120-cves-cve-2020-1337
https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2020-1383