A denial of service vulnerability exists when Windows improperly handles objects in memory. An attacker who successfully exploited the vulnerability could cause a target system to stop responding. To exploit this vulnerability, an attacker would have to log on to an affected system and run a specially crafted application or to convince a user to open a specific file on a network share. The vulnerability would not allow an attacker to execute code or to elevate user rights directly, but it could be used to cause a target system to stop responding. The update addresses the vulnerability by correcting how Windows handles objects in memory.
https://www.tenable.com/blog/tenable-roundup-for-microsofts-june-2019-patch-tuesday
https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2019-1025
https://msrc.microsoft.com/update-guide/vulnerability/CVE-2019-1025