The Microsoft Server Message Block (SMBv3) protocol is a networking communication protocol that allows file, print, and other communications between computers in a network. It is primarily used in Windows operating systems for sharing resources like files, printers, and communication devices. The SMB protocol is also important in cloud storage and can be accessed by other operating systems like Linux and macOS, which supports SMB sharing.
Recently, a severe remote code execution vulnerability, CVE-2020-0796, was detected in the Windows SMBv3 protocol. This vulnerability allows attackers to execute malicious code on target servers or clients using specially crafted packets. The threat actor can send a maliciously crafted compressed data packet which exploits the buffer overflow vulnerability and gain the ability to execute malicious code on the targeted system.
The exploitation of this vulnerability has several severe consequences. The attacker can remotely execute code to take over a system with malicious intent, encrypt the victim’s sensitive data, install malware, or even ransomware. The successful exploitation of this vulnerability can provide an attacker with complete control of the target system, including the ability to exfiltrate or alter data, abuse administrative privileges, and disrupt system integrity.
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REFERENCES
- https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2020-0796
- http://packetstormsecurity.com/files/156731/CoronaBlue-SMBGhost-Microsoft-Windows-10-SMB-3.1.1-Proof-Of-Concept.html
- http://packetstormsecurity.com/files/156732/Microsoft-Windows-SMB-3.1.1-Remote-Code-Execution.html
- http://packetstormsecurity.com/files/156980/Microsoft-Windows-10-SMB-3.1.1-Local-Privilege-Escalation.html
- http://packetstormsecurity.com/files/157110/SMBv3-Compression-Buffer-Overflow.html
- http://packetstormsecurity.com/files/157901/Microsoft-Windows-SMBGhost-Remote-Code-Execution.html
- http://packetstormsecurity.com/files/158054/SMBleed-SMBGhost-Pre-Authentication-Remote-Code-Execution-Proof-Of-Concept.html
To protect against this vulnerability, it is necessary to implement the following precautions:
- Disable SMBv3 compression.
- Block inbound and outbound connections to TCP port 445.
- Apply workarounds such as renaming or disabling the file sharing protocol.
- Keep operating systems and all software updated.
- Use a reputable and updated endpoint security solution.
- For SMB servers, you can disable compression to block unauthenticated attackers from exploiting the vulnerability against an SMBv3 Server with the PowerShell command below.
Set-ItemProperty -Path "HKLM:\SYSTEM\CurrentControlSet\Services\LanmanServer\Parameters" DisableCompression -Type DWORD -Value 1 -Forc
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