Hyper-V Critical remote code execution vulnerability in May 2021 patch Tuesday

The past few months from a security perspective have been a roller coaster of zero-day vulnerabilities and critical patches that have been needed to patch serious issues found across a wide range of Microsoft products and solutions. This has notably included Microsoft Exchange Server and others. The latest patch Tuesday from Microsoft contains some 55 security fixes, many of which are critical or high in severity. One I wanted to key in on is a Hyper-V Remote Code execution vulnerability that is a pretty nasty one that IT admins will want to make sure they get patched for business-critical Hyper-V environments. Let’s take a look at Hyper-V critical remote code execution vulnerability in May 2021 patch Tuesday and see what it involves and how to get it patched.

May 2021 Patch Tuesday Security Updates available

There is a wide range of vulnerabilities that affect various Microsoft solutions and products to be aware of. The following is a rundown of the patches and vulnerabilities contained in this Patch Tuesday as documented by Bleeping Computer.

TagCVE IDCVE TitleSeverity
.NET Core & Visual StudioCVE-2021-31204.NET and Visual Studio Elevation of Privilege VulnerabilityImportant
HTTP.sysCVE-2021-31166HTTP Protocol Stack Remote Code Execution VulnerabilityCritical
Internet ExplorerCVE-2021-26419Scripting Engine Memory Corruption VulnerabilityCritical
Jet Red and Access ConnectivityCVE-2021-28455Microsoft Jet Red Database Engine and Access Connectivity Engine Remote Code Execution VulnerabilityImportant
Microsoft Accessibility Insights for WebCVE-2021-31936Microsoft Accessibility Insights for Web Information Disclosure VulnerabilityImportant
Microsoft Bluetooth DriverCVE-2021-31182Microsoft Bluetooth Driver Spoofing VulnerabilityImportant
Microsoft Dynamics Finance & OperationsCVE-2021-28461Dynamics Finance and Operations Cross-site Scripting VulnerabilityImportant
Microsoft Exchange ServerCVE-2021-31195Microsoft Exchange Server Remote Code Execution VulnerabilityImportant
Microsoft Exchange ServerCVE-2021-31209Microsoft Exchange Server Spoofing VulnerabilityImportant
Microsoft Exchange ServerCVE-2021-31207Microsoft Exchange Server Security Feature Bypass VulnerabilityModerate
Microsoft Exchange ServerCVE-2021-31198Microsoft Exchange Server Remote Code Execution VulnerabilityImportant
Microsoft Graphics ComponentCVE-2021-31170Windows Graphics Component Elevation of Privilege VulnerabilityImportant
Microsoft Graphics ComponentCVE-2021-31188Windows Graphics Component Elevation of Privilege VulnerabilityImportant
Microsoft OfficeCVE-2021-31176Microsoft Office Remote Code Execution VulnerabilityImportant
Microsoft Office ExcelCVE-2021-31175Microsoft Office Remote Code Execution VulnerabilityImportant
Microsoft Office ExcelCVE-2021-31177Microsoft Office Remote Code Execution VulnerabilityImportant
Microsoft Office ExcelCVE-2021-31179Microsoft Office Remote Code Execution VulnerabilityImportant
Microsoft Office ExcelCVE-2021-31178Microsoft Office Information Disclosure VulnerabilityImportant
Microsoft Office ExcelCVE-2021-31174Microsoft Excel Information Disclosure VulnerabilityImportant
Microsoft Office SharePointCVE-2021-28478Microsoft SharePoint Spoofing VulnerabilityImportant
Microsoft Office SharePointCVE-2021-31181Microsoft SharePoint Remote Code Execution VulnerabilityImportant
Microsoft Office SharePointCVE-2021-26418Microsoft SharePoint Spoofing VulnerabilityImportant
Microsoft Office SharePointCVE-2021-28474Microsoft SharePoint Server Remote Code Execution VulnerabilityImportant
Microsoft Office SharePointCVE-2021-31171Microsoft SharePoint Information Disclosure VulnerabilityImportant
Microsoft Office SharePointCVE-2021-31173Microsoft SharePoint Server Information Disclosure VulnerabilityImportant
Microsoft Office SharePointCVE-2021-31172Microsoft SharePoint Spoofing VulnerabilityImportant
Microsoft Office WordCVE-2021-31180Microsoft Office Graphics Remote Code Execution VulnerabilityImportant
Microsoft Windows Codecs LibraryCVE-2021-31192Windows Media Foundation Core Remote Code Execution VulnerabilityImportant
Microsoft Windows Codecs LibraryCVE-2021-28465Web Media Extensions Remote Code Execution VulnerabilityImportant
Microsoft Windows IrDACVE-2021-31184Microsoft Windows Infrared Data Association (IrDA) Information Disclosure VulnerabilityImportant
Open Source SoftwareCVE-2021-31200Common Utilities Remote Code Execution VulnerabilityImportant
Role: Hyper-VCVE-2021-28476Hyper-V Remote Code Execution VulnerabilityCritical
Skype for Business and Microsoft LyncCVE-2021-26422Skype for Business and Lync Remote Code Execution VulnerabilityImportant
Skype for Business and Microsoft LyncCVE-2021-26421Skype for Business and Lync Spoofing VulnerabilityImportant
Visual StudioCVE-2021-27068Visual Studio Remote Code Execution VulnerabilityImportant
Visual Studio CodeCVE-2021-31214Visual Studio Code Remote Code Execution VulnerabilityImportant
Visual Studio CodeCVE-2021-31211Visual Studio Code Remote Code Execution VulnerabilityImportant
Visual Studio CodeCVE-2021-31213Visual Studio Code Remote Containers Extension Remote Code Execution VulnerabilityImportant
Windows Container Isolation FS Filter DriverCVE-2021-31190Windows Container Isolation FS Filter Driver Elevation of Privilege VulnerabilityImportant
Windows Container Manager ServiceCVE-2021-31168Windows Container Manager Service Elevation of Privilege VulnerabilityImportant
Windows Container Manager ServiceCVE-2021-31169Windows Container Manager Service Elevation of Privilege VulnerabilityImportant
Windows Container Manager ServiceCVE-2021-31208Windows Container Manager Service Elevation of Privilege VulnerabilityImportant
Windows Container Manager ServiceCVE-2021-31165Windows Container Manager Service Elevation of Privilege VulnerabilityImportant
Windows Container Manager ServiceCVE-2021-31167Windows Container Manager Service Elevation of Privilege VulnerabilityImportant
Windows CSC ServiceCVE-2021-28479Windows CSC Service Information Disclosure VulnerabilityImportant
Windows Desktop BridgeCVE-2021-31185Windows Desktop Bridge Denial of Service VulnerabilityImportant
Windows OLECVE-2021-31194OLE Automation Remote Code Execution VulnerabilityCritical
Windows Projected File System FS FilterCVE-2021-31191Windows Projected File System FS Filter Driver Information Disclosure VulnerabilityImportant
Windows RDP ClientCVE-2021-31186Windows Remote Desktop Protocol (RDP) Information Disclosure VulnerabilityImportant
Windows SMBCVE-2021-31205Windows SMB Client Security Feature Bypass VulnerabilityImportant
Windows SSDP ServiceCVE-2021-31193Windows SSDP Service Elevation of Privilege VulnerabilityImportant
Windows WalletServiceCVE-2021-31187Windows WalletService Elevation of Privilege VulnerabilityImportant
Windows Wireless NetworkingCVE-2020-24588Windows Wireless Networking Spoofing VulnerabilityImportant
Windows Wireless NetworkingCVE-2020-24587Windows Wireless Networking Information Disclosure VulnerabilityImportant
Windows Wireless NetworkingCVE-2020-26144Windows Wireless Networking Spoofing VulnerabilityImportant

Hyper-V Critical remote code execution vulnerability CVE-2021-28476

The official Hyper-V remote code execution vulnerability CVE is contained in CVE-2021-28476. The description of the vulnerability is as follows:

“Under what circumstances might this vulnerability be exploited other than as a denial of service attack against a Hyper-V host?

This issue allows a guest VM to force the Hyper-V host’s kernel to read from an arbitrary, potentially invalid address. The contents of the address read would not be returned to the guest VM. In most circumstances, this would result in a denial of service of the Hyper-V host (bugcheck) due to reading an unmapped address. It is possible to read from a memory mapped device register corresponding to a hardware device attached to the Hyper-V host which may trigger additional, hardware device specific side effects that could compromise the Hyper-V host’s security.”

Installing Security Updates with PowerShell

I really like the PSWindowsUpdate PowerShell module for installing Windows Updates. It provides a lot of great parameters to key in on specific updates and control the behavior during the install. To use the PSWindowsUpdate PowerShell module, you can use the following to install the module:

Get-PackageProvider -name nuget -force
Install-Module PSWindowsUpdate -confirm:$false -force

After installing the module, you can search for and install all security updates using the following:

Get-WindowsUpdate -MicrosoftUpdate -Category "Security Updates" -install -IgnoreUserInput -acceptall -IgnoreReboot | Out-File -filepath 'c:windowsupdate.log' -append
Using powershell to patch hyper v critical remote code vulnerability
Using powershell to patch hyper v critical remote code vulnerability

Patching your Hyper-V servers from this critical security vulnerability is something you will want to schedule as soon as possible. Even thought it isn’t at this point being exploited in the wild, there is a good chance it will be very soon.

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