Microsoft has released KB4551762 just two days after the initial KB4540673 cumulative update on March 2020 Patch Tuesday. KB4551762 is also a cumulative update. That means if you are missing any security update, you can install KB4551762 and all fixes will be installed for you.
This update only includes one fix but it is an important one. Microsoft just fixed the vulnerability in the SMBv3.1.1 feature which was introduced in Windows 10 Version 1909 and Version 1903.
Server Message Block (SMB) is a network file sharing protocol that enables network computers to read, write and request services from other network computers.
Examples of network services using SMB include Hyper-V, Microsoft SQL Server, and file sharing feature in Windows 10. SMBv3.1.1 was introduced in Windows 10 Version 1903 and is also available in Version 1909.
A vulnerability was discovered in SMBv3.1.1 exactly on the 10th of March 2020 Patch Tuesday. According to researchers, this vulnerability could affect more than 48000 computers running Windows 10 and Windows Server Version 1903/1909.
This vulnerability is named SMBGhost by the MalwareHunter team. Niall Newman also suggested disabling SMBv3 compression to stay safe from this vulnerability.
Microsoft also released a security guidance advisory to disable SMBv3 compression.
But since SMBv3.1.1 offers so much network sharing features, Microsoft does not recommend disabling the functionality permanently.
To stay safe, it is highly recommended to install KB4551762 that will fix the vulnerability.
Install KB4551762 using Windows Update
To install the latest update using Windows Update, go to Settings –> Update & Security –> Windows Update. Press the Check for Updates button. You should see at least the following updates come up:
2020-03 Cumulative Update for Windows 10 Version 1909 for x64-based Systems (KB4551762)
Press the Download button to download and install the update automatically.
Download KB4551762 Standalone installers
You can also download KB4540673 as a standalone offline installer. The benefit of this is when you have to install this update on multiple systems that do not have an active Internet connection or have limited bandwidth.
After installing this update, the Operating System build number will become 18363.720 for Windows 10 Version 1909 and 18362.720 for Windows 10 Version 1903.
Uninstall KB4551762 cumulative update
Some users are having issues with their Windows after installing this update. I forgot to mention that this update can be easily uninstalled and everything will be reverted to normal.
If you are having issues with this update, it can be uninstalled in two ways:
Uninstall KB4551762 using Windows Update History tool
Go to Windows Settings (Windows key + i) –> Update & Security –> Windows Update.
- From the right-hand pane, click on View update history.
- Now click on Uninstall updates.
- Select Update for Microsoft Windows (KB4551762) and press the Uninstall button.
Uninstall KB4551762 using command-line tools
Another quick way to uninstall this update is by using the command prompt. Here are the commands:
- Open Command Prompt (Run –> cmd)
- Run the following command:
wmic qfe list brief /format:table
This will show all the updates installed on the computer. Make sure KB4551762 is on the list.
- To uninstall the update, run the following command
wusa /uninstall /kb:4551762
Once the update is uninstalled, you will need to restart the system for the change to take effect. Hopefully, this will fix your woes but also make the computer vulnerable to SMBv3 vulnerability.