Executive Summary

Summary
Title Microsoft SMBv3 compression remote code execution vulnerability
Informations
Name VU#872016 First vendor Publication 2020-03-23
Vendor VU-CERT Last vendor Modification 2020-06-04
Severity (Vendor) N/A Revision M

Security-Database Scoring CVSS v3

Cvss vector : CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
Overall CVSS Score 10
Base Score 10 Environmental Score 10
impact SubScore 6 Temporal Score 10
Exploitabality Sub Score 3.9
 
Attack Vector Network Attack Complexity Low
Privileges Required None User Interaction None
Scope Changed Confidentiality Impact High
Integrity Impact High Availability Impact High
Calculate full CVSS 3.0 Vectors scores

Security-Database Scoring CVSS v2

Cvss vector : (AV:N/AC:L/Au:N/C:P/I:P/A:P)
Cvss Base Score 7.5 Attack Range Network
Cvss Impact Score 6.4 Attack Complexity Low
Cvss Expoit Score 10 Authentication None Required
Calculate full CVSS 2.0 Vectors scores

Detail

Overview

Microsoft SMBv3 contains a vulnerability in the handling of compression, which may allow a remote, unauthenticated attacker to execute arbitrary code on a vulnerable system. This vulnerability is being referred to as "SMBGhost and CoronaBlue."

Description

Microsoft Server Message Block 3.1.1 (SMBv3) contains a vulnerability in the way that it handles connections that use compression. This vulnerability may allow a remote, unauthenticated attacker to execute arbitrary code on a vulnerable system. It has been reported that this vulnerability is "wormable."

Impact

By connecting to a vulnerable Windows machine using SMBv3, or by causing a vulnerable Windows system to initiate a client connection to a SMBv3 server, a remote, unauthenticated attacker may be able to execute arbitrary code with SYSTEM privileges on a vulnerable system.

Solution

Apply an update

This issue has been addressed in the Microsoft update for CVE-2020-0796. Please also consider the following workarounds:

Disable SMBv3 compression

According to Microsoft Security Advisory ADV200005 :


    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 -Force

    Notes:

    1. No reboot is needed after making the change.
    2. This workaround does not prevent exploitation of SMB clients.

    You can disable the workaround with the PowerShell command below.

    Set-ItemProperty -Path "HKLM:\SYSTEM\CurrentControlSet\Services\LanmanServer\Parameters" DisableCompression -Type DWORD -Value 0 -Force

Block inbound and outbound SMB

Consider blocking outbound SMB connections (TCP port 445 for SMBv3) from the local network to the WAN. Also ensure that SMB connections from the internet are not allowed to connect inbound to an enterprise LAN.

Acknowledgements

This document was written by Will Dormann.

Original Source

Url : https://kb.cert.org/vuls/id/872016

CWE : Common Weakness Enumeration

% Id Name
100 % CWE-20 Improper Input Validation

CPE : Common Platform Enumeration

TypeDescriptionCount
Os 2
Os 2

Snort® IPS/IDS

Date Description
2020-04-14 Microsoft Windows SMB srv2.sys remote code execution attempt
RuleID : 53448 - Revision : 1 - Type : OS-WINDOWS
2020-04-14 Microsoft Windows SMB srv2.sys remote code execution attempt
RuleID : 53447 - Revision : 1 - Type : OS-WINDOWS
2020-04-14 Microsoft Windows SMB srv2.sys remote code execution attempt
RuleID : 53428 - Revision : 3 - Type : OS-WINDOWS
2020-04-14 Microsoft Windows SMB srv2.sys remote code execution attempt
RuleID : 53427 - Revision : 3 - Type : OS-WINDOWS
2020-04-14 Microsoft Windows SMB srv2.sys remote code execution attempt
RuleID : 53426 - Revision : 3 - Type : OS-WINDOWS
2020-04-14 Microsoft Windows SMB srv2.sys remote code execution attempt
RuleID : 53425 - Revision : 3 - Type : OS-WINDOWS

Alert History

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0
1
2
Date Informations
2020-06-12 21:17:42
  • Multiple Updates
2020-06-05 00:17:31
  • Multiple Updates
2020-05-23 13:15:40
  • First insertion