How to Fix CVE-2017-8540: Out-of-bounds write in Malware Protection Engine

WARNING: This vulnerability is on the CISA Known Exploited Vulnerabilities catalog (added 2022-03-03). Federal civilian agencies must remediate by 2022-03-24. Treat it as active exploitation, not theoretical.

What is CVE-2017-8540?

The Microsoft Malware Protection Engine running on Microsoft Forefront and Microsoft Defender on Microsoft Windows Server 2008 SP2 and R2 SP1, Windows 7 SP1, Windows 8.1, Windows Server 2012 Gold and R2, Windows RT 8.1, Windows 10 Gold, 1511, 1607, and 1703, and Windows Server 2016, Microsoft Exchange Server 2013 and 2016, does not properly scan a specially crafted file leading to memory corruption. aka "Microsoft Malware Protection Engine Remote Code Execution Vulnerability", a different vulnerability than CVE-2017-8538 and CVE-2017-8541.

Am I affected?

Run the version check that matches your platform:

# Windows
winget list | findstr /I "malware"
Get-WmiObject Win32_Product | Where-Object { $_.Name -like "*Malware Protection Engine*" } | Select-Object Name, Version

Compare what you see against the Affected row above (Microsoft Corporation Malware Protection Engine Microsoft Forefront and Microsoft Defender on Microsoft Windows Server 2008 SP2 and R2 SP1, Windows 7 SP1, Windows 8.1, Windows Server 2012 Gold and R2, Windows RT 8.1, Windows 10 Gold, 1511, 1607, and 1703, and Windows Server 2016, Microsoft Exchange Server 2013 and 2016.). If your build sits inside that range, you are exposed and should patch.

How to fix CVE-2017-8540

The primary fix is to upgrade Malware Protection Engine to the patched build. Use the commands for your platform below; the patched version listed in the vendor advisory is: See vendor advisory.

Windows (PowerShell, run as administrator)

# Check installed version
Get-HotFix | Sort-Object InstalledOn -Descending | Select-Object -First 5

# Apply latest Microsoft security updates (Windows Update)
Install-Module -Name PSWindowsUpdate -Force -SkipPublisherCheck
Import-Module PSWindowsUpdate
Get-WindowsUpdate -MicrosoftUpdate
Install-WindowsUpdate -MicrosoftUpdate -AcceptAll -AutoReboot

# Or via winget for application-level patches
winget upgrade --all --accept-source-agreements --accept-package-agreements

If the affected component is a third-party application, identify the package and run:

winget upgrade --id <vendor.product>

Replace <vendor.product> with the actual winget identifier (run winget search Malware Protection Engine to find it).

Complete PowerShell remediation script (Windows)

# Fix script for CVE-2017-8540 affecting Malware Protection Engine
# Run as administrator. Detect -> backup -> upgrade -> verify -> log.

$ErrorActionPreference = "Stop"
$LogPath  = "C:\Logs\CVE-2017-8540-fix-$(Get-Date -Format yyyyMMdd-HHmmss).log"
New-Item -ItemType Directory -Force (Split-Path $LogPath) | Out-Null
Start-Transcript -Path $LogPath -Append

try {
    Write-Host "[1/4] Detecting installed version of Malware Protection Engine"
    $pkg = winget list --id "Malware_Protection_Engin" 2>$null
    Write-Host $pkg

    Write-Host "[2/4] Backing up configuration"
    $backup = "C:\Backup\Malware_Protection_Engin-$(Get-Date -Format yyyyMMdd)"
    New-Item -ItemType Directory -Force $backup | Out-Null
    Get-ChildItem "C:\ProgramData\Malware_Protection_Engin" -ErrorAction SilentlyContinue |
        Copy-Item -Destination $backup -Recurse -Force -ErrorAction SilentlyContinue

    Write-Host "[3/4] Applying upgrade to latest"
    winget upgrade --id "Malware_Protection_Engin" --silent --accept-source-agreements --accept-package-agreements
    # Fallback: Windows Update for OS-level fixes
    if ($LASTEXITCODE -ne 0) {
        Install-Module -Name PSWindowsUpdate -Force -SkipPublisherCheck -ErrorAction SilentlyContinue
        Import-Module PSWindowsUpdate
        Install-WindowsUpdate -MicrosoftUpdate -AcceptAll -IgnoreReboot
    }

    Write-Host "[4/4] Verifying patched build"
    winget list --id "Malware_Protection_Engin"
    Write-Host "Fix applied. Reboot if prompted."
    exit 0
} catch {
    Write-Error "Patch failed: $_"
    exit 1
} finally {
    Stop-Transcript
}

Complete Bash remediation script (Linux)

#!/usr/bin/env bash
# Fix script for CVE-2017-8540 affecting Malware Protection Engine
# Detect -> backup -> upgrade -> verify -> log.

set -euo pipefail
LOG="/var/log/cve-2017-8540-fix-$(date +%Y%m%d-%H%M%S).log"
exec > >(tee -a "$LOG") 2>&1

echo "[1/4] Detecting installed version"
if command -v dpkg >/dev/null; then
    dpkg -s malware 2>/dev/null | grep -i version || echo "malware not installed via dpkg"
elif command -v rpm >/dev/null; then
    rpm -q malware || echo "malware not installed via rpm"
fi

echo "[2/4] Backing up configuration"
BACKUP="/root/backup-cve-2017-8540-$(date +%Y%m%d)"
mkdir -p "$BACKUP"
for d in /etc/malware /etc/malware.d /etc/malware.conf; do
    [ -e "$d" ] && cp -a "$d" "$BACKUP/" || true
done

echo "[3/4] Applying upgrade (target: latest)"
if command -v apt-get >/dev/null; then
    apt-get update
    apt-get install --only-upgrade -y malware
elif command -v dnf >/dev/null; then
    dnf upgrade --security -y malware
elif command -v yum >/dev/null; then
    yum update -y malware
elif command -v zypper >/dev/null; then
    zypper --non-interactive patch --category security
fi

echo "[4/4] Verifying patched build"
if command -v dpkg >/dev/null; then
    dpkg -s malware 2>/dev/null | grep -i version
elif command -v rpm >/dev/null; then
    rpm -q malware
fi
echo "Done. Restart any running daemons that loaded the old library."

If you can't patch immediately

If you cannot apply the patched version today, restrict exposure with one of the following runnable controls. None replace the patch.

Windows firewall isolation

# Allow only management subnet to reach the vulnerable service
New-NetFirewallRule -DisplayName "Restrict Malware Protection Engine" `
    -Direction Inbound -Action Block -RemoteAddress Any `
    -Protocol TCP -LocalPort 443
New-NetFirewallRule -DisplayName "Allow Mgmt Malware Protection Engine" `
    -Direction Inbound -Action Allow -RemoteAddress 10.0.0.0/8 `
    -Protocol TCP -LocalPort 443

Service-level fallback

# If the affected feature is optional, stop the service until the patch is applied
sudo systemctl stop malware
sudo systemctl disable malware

How to verify the fix worked

# Linux
malware --version 2>/dev/null || dpkg -s malware | grep -i version
rpm -q malware 2>/dev/null || true

# Windows
winget list | findstr /I "malware"
Get-HotFix | Sort-Object InstalledOn -Descending | Select-Object -First 5

Expected: the reported version is at or above the patched build documented in the advisory. Restart any services that loaded the old library (systemctl restart <service> on Linux, restart the Windows service or reboot when prompted). For network appliances, run show version on the device and confirm the build matches the patched release.

Frequently asked questions

Related fixes

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

• How to Fix CVE-2017-0149: Out-of-Bounds Write in Microsoft Internet Explorer — Out-of-Bounds Write in Microsoft Internet Explorer
• How to Fix CVE-2017-0213: Elevation of Privilege in Microsoft Windows — Elevation of Privilege in Microsoft Windows
• How to Fix CVE-2017-0148: Improper Input Validation in Microsoft SMBv1 server , Improper Input Validation in Microsoft SMBv1 server
• How to Fix CVE-2017-0147: Information Disclosure in Microsoft SMBv1 server , Information Disclosure in Microsoft SMBv1 server
• How to Fix CVE-2017-0210: Elevation of Privilege in Microsoft Internet Explorer , Elevation of Privilege in Microsoft Internet Explorer

Is CVE-2017-8540 actually being exploited?

According to the data sources above, yes, CISA has it listed as actively exploited. Either way, the fix is the same: apply the vendor patch.

Do I need to reboot after patching?

For OS or kernel updates, yes. For most userland packages a systemctl restart <service> is enough. Any process that loaded the old shared library keeps using it until restarted, so when in doubt, reboot.

What is the CVSS score?

7.8 (high). Refer to the vendor advisory for the exact vector string.

Where is the official advisory?

See the References section at the bottom of this page; the vendor's URL is the authoritative source for affected builds and patched versions.

References

• Official vendor advisory: https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2017-8540
• NVD: https://nvd.nist.gov/vuln/detail/CVE-2017-8540
• CISA KEV catalog entry: https://www.cisa.gov/known-exploited-vulnerabilities-catalog
• http://www.securityfocus.com/bid/98703
• https://www.exploit-db.com/exploits/42088/
• http://www.securitytracker.com/id/1038571
• https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2017-8540

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