Microsoft patched a critical Remote Code Execution Vulnerability with Windows SMBv3 Client/Server that allows an attacker to execute code remotely.

The flaw can be tracked as CVE-2020-0796 and the flaw impacts only Windows 10 Version and Windows Server Version 1903. It was leaked accidentally as part of the March 2020 Patch Tuesday update.

SMBv3 RCE Flaw

The vulnerability resides in the way that certain requests handled by Microsoft Server Message Block 3.1.1. An attacker exploiting the vulnerability can gain the ability to execute code on the target SMB Server or SMB Client.

Now the vulnerability patched by Microsoft, server administrators are recommended to apply the patches to protect the networks.

According to the scan run by Kryptos Logic more than 48000 vulnerable hosts were identified. Kryptos Logic also added that they have developed a basic PoC.

“To exploit the vulnerability against an SMB Server, an unauthenticated attacker could send a specially crafted packet to a targeted SMBv3 server. 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,” reads Microsoft document.

Microsoft also stated that the vulnerability was not yet exploited in the wild and the details not publically disclosed.

Affected versions

The vulnerability affects Windows 10 Version desktop version and the Windows Server Version 1903.

• Windows 10 Version 1903 for 32-bit Systems
• Windows 10 Version 1903 for x64-based Systems
• Windows 10 Version 1903 for ARM64-based Systems
• Windows Server, version 1903 (Server Core installation)
• Windows 10 Version 1909 for 32-bit Systems
• Windows 10 Version 1909 for x64-based Systems
• Windows 10 Version 1909 for ARM64-based Systems
• Windows Server, version 1909 (Server Core installation)