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Unpatched Critical Windows SMBv3 Flaw Disclosed by Microsoft | Cyberops

Unpatched Critical Windows SMBv3 Flaw Disclosed by Microsoft

By Aneesh A S 0 Comment March 12, 2020

Microsoft issued an advisory warning its Windows users of a new critical, unpatched, and wormable vulnerability affecting Server Message Block 3.0 (SMBv3) network communication protocol reported as part of the March 2020 Patch Tuesday update.

Server Message Block protocol is used for file sharing, network browsing, printing services, and interprocess communication over a network.

Microsoft planned to fix the flaw with the March 2020 Patch Tuesday update but did not fix and ended up accidentally leaking the existence of the unpatched flaw.

The flaw ( CVE-2020-0796), if exploited , could allow an attacker to execute code on the target SMB Server or SMB Client. The vulnerability occurs in a way as to how the  software handles the malicious request crafted through a compressed data packet. An unauthenticated attacker could exploit the vulnerability within the context of the application successfully and gain control over the system.

Affected versions

  •     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) 

A researcher ‘ollypwn’ posted a tool via Twitter to check if servers are vulnerable or not.

Since there is not a patch that is currently available and it’s unclear when Microsoft plans to release the patch, the company is urging users to disable SMBv3 compression and block TCP port 445 on firewalls and client computers preventing attackers from initiating the connection with the vulnerable machine.

UPDATE :

Microsoft has released the patch for the critical Remote Code Execution Vulnerability that affects Windows SMBv3 Client/Server.

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