Patch

CVE-2021-43890

with vRx

Vulnerability Overview

CVE Name

CVE-2021-43890

Severity

7.1

High

CVE Description

We have investigated reports of a spoofing vulnerability in AppX installer that affects Microsoft Windows. Microsoft is aware of attacks that attempt to exploit this vulnerability by using specially crafted packages that include the malware family known as...

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Latest Patch info

Patch Name

https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-43890

Date

15.12.2021

Script

Script Type

Remediation script

Copy script

This script will mitigate the CVE-2021-43890 according to the official mitigation instructions at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-43890 by automating the mitigation instructions & process. More about CVE-2021-43890: https://nvd.nist.gov/vuln/detail/CVE-2021-43890

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# Check if the script is running with administrator privileges
$isAdmin = ([Security.Principal.WindowsPrincipal] [Security.Principal.WindowsIdentity]::GetCurrent()).IsInRole([Security.Principal.WindowsBuiltInRole]::Administrator)
if (-not $isAdmin) {
    Write-Host "[-] Script must be run with administrator privileges."
    exit
}

# Enable to block non-admin user app installations
$blockNonAdminUserInstall = "HKLM:\SOFTWARE\Policies\Microsoft\Windows\Installer"
Set-ItemProperty -Path $blockNonAdminUserInstall -Name "BlockNonAdminUserInstall" -Value 1 -Type DWord -Force

# Enable to prevent installing apps from outside the Microsoft Store
$preventInstallingApps = "HKLM:\SOFTWARE\Policies\Microsoft\Windows\Store"
Set-ItemProperty -Path $preventInstallingApps -Name "AllowNonStoreAppInstallation" -Value 0 -Type DWord -Force

# Check if the GPO settings were applied successfully
$blockNonAdminValue = (Get-ItemProperty -Path $blockNonAdminUserInstall -Name "BlockNonAdminUserInstall").BlockNonAdminUserInstall
$allowNonStoreValue = (Get-ItemProperty -Path $preventInstallingApps -Name "AllowNonStoreAppInstallation").AllowNonStoreAppInstallation

if ($blockNonAdminValue -eq 1 -and $allowNonStoreValue -eq 0) {
    Write-Host "[+] GPO settings applied successfully. Non-admin users are now blocked from installing Windows app packages."
    Write-Host "[+] Installing apps from outside the Microsoft Store is also blocked."
} else {
    Write-Host "[-] Failed to apply GPO settings. Please check if the script is running with administrator privileges."
}

Copy script

Affected OS & Apps

APP Installer

Microsoft

Windows 10 21H2

Microsoft

Windows 10 1507

Microsoft

APP Installer

Microsoft

Windows 10 21H2

Microsoft

Windows 10 1507

Microsoft

Windows 10 1809

Microsoft

Windows 11 21H2

Microsoft

Windows 10 21H1

Microsoft

Windows 10 20H2

Microsoft

Windows 10 2004

Microsoft

Windows 10 1909

Microsoft

Windows 10 1903

Microsoft

Windows 10 1803

Microsoft

Windows 10 1709

Microsoft

Windows 10

Microsoft

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