A remote code execution vulnerability exists when the Microsoft Speech API (SAPI) improperly handles text-to-speech (TTS) input. The vulnerability could corrupt memory in a way that enables an attacker to execute arbitrary code in the context of the current user. To exploit the vulnerability, an attacker would need to convince a user to open a specially crafted document containing TTS content invoked through a scripting language. The update address the vulnerability by modifying how the system 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-2019-0985
https://msrc.microsoft.com/update-guide/vulnerability/CVE-2019-0985