A denial of service exists in Microsoft IIS Server when the optional request filtering feature improperly handles requests. An attacker who successfully exploited this vulnerability could perform a temporary denial of service against pages configured to use request filtering. To exploit this vulnerability, an attacker could send a specially crafted request to a page utilizing request filtering. The update addresses the vulnerability by changing the way certain requests are processed by the filter.
https://www.tenable.com/blog/tenable-roundup-for-microsofts-june-2019-patch-tuesday
https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2019-0941
https://msrc.microsoft.com/update-guide/vulnerability/CVE-2019-0941