https://www.bleepingcomputer.com/news/security/microsoft-leaks-info-on-wormable-windows-smbv3-cve-2020-0796-flaw/

Microsoft leaked info on a security update for a 'wormable' pre-auth remote code execution vulnerability found in the Server Message Block 3.0 (SMBv3) network communication protocol that reportedly should have been disclosed as part of this month's Patch Tuesday.

The vulnerability is due to an error when the SMBv3 handles maliciously crafted compressed data packets and it allows remote, unauthenticated attackers that exploit it to execute arbitrary code within the context of the application.