Microsoft Windows Win32k Kernel-Mode Driver Local Privilege Escalation Vulnerability (CVE-2016-0167, MS16-039)
Executive & SecOps Summary
SECOPS ASSESSMENTWindows Vista SP2, 7 SP1, 8.1, 10, Windows Server 2008, 2012 R2, and other legacy Windows OS versions
Local attackers can execute arbitrary code in kernel mode (SYSTEM privileges) via a crafted application, leading to full system compromise
Apply the official Microsoft MS16-039 security patch immediately and restrict local execution privileges on unpatched systems
Affected Products & Version Scope
Remediation & Live Workaround Commands
PATCH & WORKAROUND1. Official Patch & Version Upgrade Commands
Deploy the MS16-039 security update to remediate this vulnerability. For managed environments, use the following PowerShell commands to force update installation.
# Install and force Windows Update for the specific KB associated with MS16-039
Install-Module PSWindowsUpdate -Force -Verbose
Get-WindowsUpdate -KBArticleID KB3146706 -Install -AcceptAll -AutoReboot2. Temporary Workaround & Hardening Configuration
If patching cannot be applied immediately, restrict execution of untrusted binaries using AppLocker and enforce least privilege access control.
# Enable and start Application Identity Service for AppLocker enforcement
Set-Service -Name AppIDSvc -StartupType Automatic
Start-Service -Name AppIDSvc3. Log Audit & IoC Verification Commands
Verify the patch level by checking the file version of win32k.sys on the target system.
# Check win32k.sys file version to verify patch status
$Path = '${env:SystemRoot}\System32\win32k.sys'
if (Test-Path $Path) {
$Version = (Get-Item $Path).VersionInfo.FileVersion
Write-Output 'The current win32k.sys version is: $Version'
} else {
Write-Warning 'Target system file win32k.sys was not found.'
}Block Kernel Privilege Escalation & Ransomware Payloads Before You Can Reboot
Protect unpatched Windows, Linux, and macOS workloads against in-memory exploitation and lateral movement with autonomous EDR.
Technical Root Cause & Exploitation Mechanics
1. Vulnerability Overview & Root Cause
This vulnerability (CVE-2016-0167) is a Use-After-Free (UAF) flaw in the Windows kernel-mode driver win32k.sys. It occurs when the driver improperly handles window and menu objects in memory. When a user-mode application triggers specific API calls, the kernel initiates a callback to user space. If the application manipulates or destroys the associated object during this callback, the kernel continues to use the stale pointer upon return, leading to memory corruption.
2. Exploitation Mechanics & Attack Scenario
An attacker with local access executes a specially crafted binary designed to hook window messages (e.g., using SetWindowsHookEx). During the rendering or destruction of a menu object, the exploit intercepts the execution flow via a user-mode callback. The exploit then frees the target memory block and sprays the heap to occupy the freed address with a controlled, fake object structure. When the kernel resumes and dereferences the pointer, it executes the attacker's payload with SYSTEM privileges.
3. Infrastructure & Business Impact
As a CISA KEV-listed vulnerability, CVE-2016-0167 has been actively exploited in targeted APT campaigns. Successful exploitation bypasses all operating system security boundaries, allowing an attacker who has gained initial low-privilege access to escalate to SYSTEM. This enables credential dumping, disabling of security controls, and lateral movement across the enterprise network.
Official Vendor Advisories & References
The kernel-mode driver in Microsoft Windows Vista SP2, Windows Server 2008 SP2 and R2 SP1, Windows 7 SP1, Windows 8.1, Windows Server 2012 Gold and R2, Windows RT 8.1, and Windows 10 Gold and 1511 allows local users to gain privileges via a crafted application, aka "Win32k Elevation of Privilege Vulnerability," a different vulnerability than CVE-2016-0143 and CVE-2016-0165.
Frequently Asked SecOps Questions (CVE-2016-0167)
FAQQ1. How critical is CVE-2016-0167 and is it actively exploited in the wild?
CVE-2016-0167 is rated CVSS 7.8 (HIGH) with a 30-day EPSS exploitation probability of 5.7%. It is listed in the CISA Known Exploited Vulnerabilities (KEV) catalog, requiring immediate emergency remediation.
Q2. Which vendors and products are affected by CVE-2016-0167?
Primary impacted vendors include microsoft across windows, windows_server. Scope summary: Windows Vista SP2, Windows Server 2008 SP2/R2 SP1, Windows 7 SP1, Windows 8.1, Windows Server 2012 Gold/R2, Windows RT 8.1, Windows 10 Gold/1511
Q3. What temporary mitigations or workarounds exist for CVE-2016-0167 before patching?
[Mitigation] Apply the official Microsoft MS16-039 security patch immediately and restrict local execution privileges on unpatched systems Follow the CLI remediation commands and interactive SecOps checklist on this page to restrict exposure prior to your maintenance window.
Generate an Internal Engineering Notice or CISO Report for CVE-2016-0167
Instantly format this advisory into an executive CISO summary or engineering patch ticket.
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