CVE-2026-32201: Microsoft April 2026 Patch Tuesday Analysis and Remediation Guide

---
title: Potential Exploitation of AppLocker Filter Driver - CVE-2026-32201
id: 8a1b2c3d-4e5f-6789-0abc-1def2a3b4c5d
status: experimental
description: Detects suspicious process interactions or handle operations targeting the AppLocker Filter Driver, often indicative of EoP attempts.
references:
  - https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-32201
author: Security Arsenal
date: 2026/04/08
tags:
  - attack.privilege_escalation
  - attack.t1068
logsource:
  category: process_creation
  product: windows
detection:
  selection:
    CommandLine|contains:
      - 'applockerfltr.sys'
      - '\\??\\C:\\Windows\\System32\\drivers\\applockerfltr.sys'
    or
  selection_sysmon:
    TargetImage|contains: 'applockerfltr.sys'
  condition: 1 of selection*
falsepositives:
  - Legitimate driver debugging (rare)
level: high
---
title: Suspicious Child Process of Desktop Window Manager (dwm.exe)
id: 9b2c3d4e-5f6a-7890-1bcd-2ef3a4b5c6d7
status: experimental
description: Detects unusual child processes spawned by dwm.exe, which may indicate exploitation of the Desktop Window Manager component.
references:
  - https://attack.mitre.org/techniques/T1055/
author: Security Arsenal
date: 2026/04/08
tags:
  - attack.privilege_escalation
  - attack.defense_evasion
  - attack.t1055.001
logsource:
  category: process_creation
  product: windows
detection:
  selection_parent:
    ParentImage|endswith: '\dwm.exe'
  selection_child:
    Image|endswith:
      - '\powershell.exe'
      - '\cmd.exe'
      - '\wscript.exe'
      - '\cscript.exe'
  filter:
    User|contains: 'DWM-'
  condition: selection_parent and selection_child and not filter
falsepositives:
  - Rare; some accessibility tools may spawn scripts from DWM context.
level: high

// Hunt for suspicious process interactions involving AppLocker driver or DWM
let SuspiciousProcs = materialize(
    DeviceProcessEvents
    | where FileName in~("powershell.exe", "cmd.exe", "powershell_ise.exe")
    | where InitiatingProcessFileName =~ "dwm.exe" 
       or InitiatingProcessCommandLine contains "applockerfltr.sys"
);
SuspiciousProcs
| project Timestamp, DeviceName, AccountName, FileName, ProcessCommandLine, InitiatingProcessFileName, InitiatingProcessId, SHA256
| extend IoC = "Potential CVE-2026-32201 Exploitation"

-- Hunt for the specific driver version and suspicious process lineage
SELECT 
    OSPath.Basename, 
    Mtime, 
    Size, 
    Version.StringCompany, 
    Version.StringFileVersion 
FROM glob(globs="C:\\Windows\\System32\\drivers\\applockerfltr.sys")
WHERE Mtime < timestamp("2026-04-08") 
  -- This identifies the vulnerable driver version before the patch date

-- Hunt for unusual child processes of dwm.exe
SELECT Pid, Ppid, Name, Exe, Cmdline, Username
FROM pslist()
WHERE Ppid IN (SELECT Pid FROM pslist() WHERE Name =~ "dwm.exe")
  AND Name IN ("cmd.exe", "powershell.exe", "python.exe", "wscript.exe")
  AND NOT Name =~ "dwm.exe"

# Script to verify the installation of the April 2026 Patch Tuesday updates
# Specifically targeting the OS Build and AppLocker Driver version

Write-Host "[+] Checking for April 2026 Security Updates..." -ForegroundColor Cyan

# Check OS Build Number (Placeholder for the specific Build Revision expected in April 2026)
# Adjust the BuildNumber based on the specific KB release (e.g., KB504xxxx)
$CurrentBuild = [System.Environment]::OSVersion.Version
$ExpectedBuildMinor = 20348 # Example for Server 2022, adjust for Win 10/11

Write-Host "[*] Current OS Build: $($CurrentBuild)" 

# Check AppLocker Driver File Version
$DriverPath = "C:\Windows\System32\drivers\applockerfltr.sys"
if (Test-Path $DriverPath) {
    $DriverInfo = Get-Item $DriverPath
    Write-Host "[*] AppLocker Driver Last Modified: $($DriverInfo.LastWriteTime)"
    
    # If modified before April 2026, it is likely vulnerable
    if ($DriverInfo.LastWriteTime -lt [DateTime]"2026-04-14") {
        Write-Host "[!] ALERT: The AppLocker driver appears out of date. CVE-2026-32201 may be applicable." -ForegroundColor Red
    } else {
        Write-Host "[+] AppLocker Driver appears patched." -ForegroundColor Green
    }
}

# Check for specific KB (Replace KB504xxxx with actual April 2026 ID)
$GetKB = Get-HotFix | Where-Object { $_.HotFixID -like "KB504xxxx" }
if (-not $GetKB) {
    Write-Host "[!] April 2026 Security Update (KB504xxxx) NOT found. Please run Windows Update immediately." -ForegroundColor Red
} else {
    Write-Host "[+] April 2026 Security Update found." -ForegroundColor Green
}