How to Fix CVE-2020-1472: Netlogon Elevation of Privilege in Windows Server version 2004

Related fixes

Other vulnerabilities in the same area that are worth patching alongside this one:

• How to Fix CVE-2020-0986: Elevation of Privilege in Windows — Elevation of Privilege in Windows
• How to Fix CVE-2020-1027: Out-of-Bounds Write in Microsoft Windows — Out-of-Bounds Write in Microsoft Windows
• How to Fix CVE-2020-1020: Remote Code Execution in Windows , Remote Code Execution in Windows
• How to Fix CVE-2020-1054: Elevation of Privilege in Windows , Elevation of Privilege in Windows
• How to Fix CVE-2020-1380: Scripting Engine Memory Corruption in Internet Explorer 11 , Scripting Engine Memory Corruption in Internet Explorer 11

*By Sai Kiran Pandrala*

⚠️ Patch immediately. CVE-2020-1472 is in CISA's Known Exploited Vulnerabilities catalog (added 2021-11-03). Federal agencies had until 2022-05-03 to remediate.

What is CVE-2020-1472?

An elevation of privilege vulnerability exists when an attacker establishes a vulnerable Netlogon secure channel connection to a domain controller, using the Netlogon Remote Protocol (MS-NRPC). An attacker who successfully exploited the vulnerability could run a specially crafted application on a device on the network. To exploit the vulnerability, an unauthenticated attacker would be required to use MS-NRPC to connect to a domain controller to obtain domain administrator access.

In practical terms, a successful attacker gets elevation of privilege to administrator or root on the affected host. CISA has confirmed exploitation in the wild, so this is not a theoretical risk.

Am I affected?

You're affected if you run Microsoft Windows Server version 2004 at any version in the Affected row above. Use these probes to find your installed build:

[System.Environment]::OSVersion.Version
Get-HotFix | Sort-Object InstalledOn -Descending | Select-Object -First 10

How to fix CVE-2020-1472

The primary fix is to upgrade to the patched build listed in the Fixed in row above (See vendor advisory). Pick the platform that matches your install and run the commands below.

Windows / Windows Server (PowerShell, admin)

# Apply the most recent cumulative update
Install-Module -Name PSWindowsUpdate -Force -Scope CurrentUser
Import-Module PSWindowsUpdate
Get-WindowsUpdate -MicrosoftUpdate -AcceptAll -Install -AutoReboot

Or install a specific KB manually

$kb = 'KB-from-advisory'   # replace with the KB ID listed in the MSRC advisory
$msu = "$env:TEMP\$kb.msu"
Invoke-WebRequest -Uri "https://catalog.update.microsoft.com/Search.aspx?q=$kb" -UseBasicParsing
# Download the matching .msu from the catalog, then:
Start-Process -FilePath 'wusa.exe' -ArgumentList "$msu /quiet /norestart" -Wait
Restart-Computer -Force

PowerShell script (Windows) - detect, back up, upgrade, verify, log

# Vendor advisory: https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2020-1472
# Run as Administrator
$ErrorActionPreference = 'Stop'
$log = "$env:ProgramData\WindowsServerversion2004-Patch-CVE-2020-1472.log"
function Write-Log($msg) { "$(Get-Date -Format s)  $msg" | Tee-Object -FilePath $log -Append }

Write-Log "Starting CVE-2020-1472 remediation for Microsoft Windows Server version 2004"

# 1. Detect: replace the path/version probe with one valid for your install
$installed = (Get-WmiObject -Class Win32_Product |
    Where-Object { $_.Name -like '*Windows*' } |
    Select-Object -First 1 -ExpandProperty Version)
Write-Log "Detected version: $installed"

if (-not $installed) {
    Write-Log "Product not installed on this host; nothing to do."
    return
}
if ([version]$installed -ge [version]'<patched-version>') {
    Write-Log "Already at fixed version $installed; no action needed."
    return
}

# 2. Backup configuration to a timestamped folder
$backup = "$env:ProgramData\WindowsServerversion2004-Backup-$(Get-Date -Format yyyyMMdd-HHmm)"
New-Item -ItemType Directory -Path $backup -Force | Out-Null
# Adjust the source path to match your install
$src = "$env:ProgramFiles\Microsoft\Windows Server version 2004"
if (Test-Path $src) { Copy-Item -Path $src -Destination $backup -Recurse -Force }
Write-Log "Backed up config to $backup"

# 3. Apply the patched installer (place the verified file on a share or staging path)
$installer = "$env:TEMP\WindowsServerversion2004-<patched-version>.msi"
if (-not (Test-Path $installer)) {
    throw "Patched installer not found at $installer. Stage it from your software repo first."
}
Start-Process msiexec.exe -ArgumentList "/i `"$installer`" /qn /norestart" -Wait
Write-Log "Installer finished"

# 4. Verify
$verify = (Get-WmiObject -Class Win32_Product |
    Where-Object { $_.Name -like '*Windows*' } |
    Select-Object -First 1 -ExpandProperty Version)
if ([version]$verify -ge [version]'<patched-version>') {
    Write-Log "SUCCESS: now at $verify (>= <patched-version>)"
} else {
    Write-Log "FAILURE: still at $verify after install"
    exit 1
}

Bash script (Linux) - detect, back up, upgrade, verify, log

# Vendor advisory: https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2020-1472
#!/usr/bin/env bash
set -euo pipefail
LOG=/var/log/windows-server-version-2004-patch-cve-2020-1472.log
log()  { echo "$(date -Iseconds)  $*" | tee -a "$LOG"; }

log "Starting CVE-2020-1472 remediation for Microsoft Windows Server version 2004"

# 1. Detect installed version (works for deb and rpm packages)
if command -v dpkg >/dev/null && dpkg -s windows-server-version-2004 >/dev/null 2>&1; then
    CURRENT=$(dpkg-query -W -f='${Version}' windows-server-version-2004)
    PKG_MGR=apt
elif command -v rpm >/dev/null && rpm -q windows-server-version-2004 >/dev/null 2>&1; then
    CURRENT=$(rpm -q --queryformat '%{VERSION}' windows-server-version-2004)
    PKG_MGR=dnf
else
    log "windows-server-version-2004 not installed via apt or rpm; check your package manager or vendor instructions."
    exit 0
fi
log "Detected: windows-server-version-2004=$CURRENT (manager=$PKG_MGR)"

# 2. Backup config
BACKUP=/var/backups/windows-server-version-2004-$(date +%Y%m%d-%H%M)
mkdir -p "$BACKUP"
for d in /etc/windows-server-version-2004 /etc/${pkg%%-*} ; do
    [ -d "$d" ] && cp -a "$d" "$BACKUP/" && log "Backed up $d to $BACKUP"
done

# 3. Upgrade
if [ "$PKG_MGR" = apt ]; then
    sudo apt-get update -y
    sudo apt-get install --only-upgrade -y windows-server-version-2004
else
    sudo dnf upgrade --security -y windows-server-version-2004
fi

# 4. Verify
if [ "$PKG_MGR" = apt ]; then
    NEW=$(dpkg-query -W -f='${Version}' windows-server-version-2004)
else
    NEW=$(rpm -q --queryformat '%{VERSION}' windows-server-version-2004)
fi
log "After upgrade: $NEW"

# Optionally compare against <patched-version> with dpkg --compare-versions or sort -V
log "Done. Restart the affected service if the package install did not."

Marquee detail: Zerologon

Zerologon (CVE-2020-1472) is a privilege escalation against the Netlogon Remote Protocol on Windows Server domain controllers. The flaw lets an unauthenticated attacker on the network reset the domain controller's machine account password to all zeros and then take over the entire domain. Microsoft shipped a two-stage rollout: the August 2020 update enforces secure RPC for machine accounts, and the February 2021 update flips secure-RPC enforcement on for everything else.

Detection script (PowerShell, run on a domain controller)

# Confirm the Netlogon registry hardening is in place after the August 2020 update
$key = 'HKLM:\SYSTEM\CurrentControlSet\Services\Netlogon\Parameters'
$val = (Get-ItemProperty -Path $key -Name 'FullSecureChannelProtection' -ErrorAction SilentlyContinue).FullSecureChannelProtection
if ($val -eq 1) {
    Write-Host "FullSecureChannelProtection enforced -- Zerologon mitigation active"
} else {
    Write-Warning "FullSecureChannelProtection NOT enforced. Set it to 1 after confirming all DCs and non-Windows devices have been patched or whitelisted."
}

# Confirm all domain controllers have the patch installed
Get-ADDomainController -Filter * | ForEach-Object {
    $hf = Invoke-Command -ComputerName $_.HostName -ScriptBlock {
        Get-HotFix | Where-Object { $_.HotFixID -in @('KB4565349','KB4571756','KB4571719','KB4571694','KB4577668','KB4601345','KB4601318','KB4601315','KB4601319','KB4601348','KB4601331','KB4601354') }
    } -ErrorAction SilentlyContinue
    [pscustomobject]@{
        DC = $_.HostName
        ZerologonKB = if ($hf) { ($hf.HotFixID -join ',') } else { 'MISSING' }
    }
}

Enforcement registry change (after all clients are compliant)

New-ItemProperty -Path 'HKLM:\SYSTEM\CurrentControlSet\Services\Netlogon\Parameters' \
    -Name 'FullSecureChannelProtection' -Value 1 -PropertyType DWord -Force
Restart-Service Netlogon

Watch for exploitation attempts

The patched Netlogon writes Event IDs 5827, 5828, 5829 (allowed vulnerable connections) and 5830, 5831 (denied connections) to the System log. Pull them with PowerShell:

Get-WinEvent -FilterHashtable @{LogName='System'; Id=5827,5828,5829,5830,5831} -MaxEvents 200 |
    Format-Table TimeCreated, Id, Message -Wrap

Any 5829 entry from a host you don't recognize warrants investigation.

If you can't patch immediately

These are runnable hardening commands. They reduce blast radius but they're not a replacement for the vendor patch.

No official vendor workaround is published for this CVE; patching is the only documented fix. The runnable hardening below is generic defense in depth, not a substitute for the patch.

Restrict the affected service to trusted networks (Linux):

# Vendor advisory: https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2020-1472
# Replace <port> with the affected service port and 10.0.0.0/24 with your admin subnet
sudo iptables -A INPUT -p tcp --dport <port> -s 10.0.0.0/24 -j ACCEPT
sudo iptables -A INPUT -p tcp --dport <port> -j DROP

Windows Firewall equivalent:

# Vendor advisory: https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2020-1472
New-NetFirewallRule -DisplayName 'Allow affected service from admin subnet' \
    -Direction Inbound -Action Allow -Protocol TCP -LocalPort <port> -RemoteAddress 10.0.0.0/24
New-NetFirewallRule -DisplayName 'Block affected service from everywhere else' \
    -Direction Inbound -Action Block -Protocol TCP -LocalPort <port>

How to verify the fix worked

Run the version probe again and confirm the running build matches the Fixed in row above.

Get-HotFix | Sort-Object InstalledOn -Descending | Select-Object -First 5

Expected output: the KB ID listed in the vendor advisory appears with an InstalledOn date that matches your patch window.

Then re-run any vulnerability scanner you used previously and confirm the finding for CVE-2020-1472 has cleared. Sweep your logs for the indicators of compromise listed in the vendor or CISA advisory, especially if the system was internet-reachable during the disclosure window.

Frequently asked questions

Is CVE-2020-1472 being actively exploited?

Yes. CISA added it to the Known Exploited Vulnerabilities catalog, which means in-the-wild exploitation has been observed and confirmed.

How severe is CVE-2020-1472?

CVSS rates it 5.5 (Medium). Use that score to set your patch priority next to the other items in your queue.

Do I have to take Windows Server version 2004 offline to apply the patch?

It depends on the deployment. High-availability or clustered installs can usually patch one node at a time with no full outage. Standalone installs typically need a short restart. Always follow the vendor's documented upgrade steps.

What if my vulnerability scanner still flags CVE-2020-1472 after I patch?

Re-run the scan after a service restart, then confirm the scanner's plugin set is up to date. Some scanners detect by banner version only and lag the official fix metadata by a release.

References

• Official vendor advisory: https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2020-1472
• NVD: https://nvd.nist.gov/vuln/detail/CVE-2020-1472
• CISA KEV catalog: https://www.cisa.gov/known-exploited-vulnerabilities-catalog
• Additional reference: https://www.kb.cert.org/vuls/id/490028
• Additional reference: http://www.openwall.com/lists/oss-security/2020/09/17/2
• Additional reference: https://usn.ubuntu.com/4510-1/

*Written by Sai Kiran Pandrala on 2026-05-25. Sourced from the official vendor advisory, the NVD record, and the CISA KEV listing. Always confirm against the vendor advisory before applying changes in production.*