Warning — Unpatched Critical ‘Wormable’ Windows SMBv3 Flaw Disclosed

Shortly after releasing its monthly batch of security updates, Microsoft late yesterday separately issued an advisory warning billions of its Windows users of a new critical, unpatched, and wormable vulnerability affecting Server Message Block 3.0 (SMBv3) network communication protocol.

It appears Microsoft originally planned to fix the flaw as part of its March 2020 Patch Tuesday update only, but, for some reason, it pulled the plug at the last minute, which apparently did not stop a tech company from accidentally leaking the existence of the unpatched flaw.

The yet-to-be patched flaw (tracked as CVE-2020-0796), if exploited successfully, could allow an attacker to execute arbitrary code on the target SMB Server or SMB Client.

The belated acknowledgment from Microsoft led some researchers to call the bug “SMBGhost.”

“To exploit the vulnerability against an SMB Server, an unauthenticated attacker could send a specially crafted packet to a targeted SMBv3 Server,” Microsoft disclosed in an advisory. “To exploit the vulnerability against an SMB Client, an unauthenticated attacker would need to configure a malicious SMBv3 Server and convince a user to connect to it.”

Server Message Block protocol provides the basis for file sharing, network browsing, printing services, and interprocess communication over a network.