Microsoft Windows win32k.sys Kernel-Mode Driver Local Privilege Escalation (CVE-2015-1701, MS15-051)
Executive & SecOps Summary
SECOPS ASSESSMENTMicrosoft Windows Server 2003 SP2, Windows Vista SP2, and Server 2008 SP2.
Local attackers can execute a specially crafted application to elevate privileges to SYSTEM, gaining full control of the target host.
Apply the official Microsoft MS15-051 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
Apply the official MS15-051 security update provided by Microsoft. For standalone installations on legacy systems, use the Windows Update Standalone Installer (wusa.exe):
:: Install the MS15-051 security update (e.g., KB3057191) silently
wusa.exe C:\Patches\Windows6.1-KB3057191-x64.msu /quiet /norestart2. Temporary Workaround & Hardening Configuration
If immediate patching is not feasible, restrict local execution privileges and enforce strict AppLocker or Software Restriction Policies to prevent unauthorized binaries from running.
# Check and enforce AppLocker rules to restrict execution of untrusted binaries
# Ensure to test these rules in a staging environment before production deployment
Import-Module AppLocker
Set-AppLockerPolicy -XMLPolicy C:\Policies\AppLockerRestriction.xml -Merge3. Log Audit & IoC Verification Commands
Verify the file version of win32k.sys to ensure the system is running the patched version of the driver.
# Retrieve the file version of win32k.sys to verify patch status
$Path = '${env:SystemRoot}\System32\win32k.sys'
if (Test-Path $Path) {
$Info = (Get-Item $Path).VersionInfo
Write-Output 'File Version: ' $Info.FileVersion
Write-Output 'Product Version: ' $Info.ProductVersion
}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 exists in the Windows kernel-mode driver win32k.sys due to improper handling of window objects and callback mechanisms in memory. During user-mode to kernel-mode transitions, certain system calls trigger user-mode callbacks without sufficient validation, leading to state desynchronization or Use-After-Free (UAF) conditions where kernel structures are corrupted or reference freed memory addresses.
2. Exploitation Mechanics & Attack Scenario
An attacker with local access executes a malicious application designed to trigger a user-mode hook callback during the execution of xxxSendMessage or similar functions within win32k.sys. While the callback is active, the attacker modifies the properties of the target window object, redirecting kernel pointers to an attacker-controlled memory space. Upon returning to kernel mode, win32k.sys trusts the corrupted pointer, executing shellcode that performs token stealing to replace the attacker's process token with the SYSTEM token.
3. Infrastructure & Business Impact
This vulnerability has been actively exploited in the wild by advanced persistent threat (APT) groups and is listed in the CISA KEV catalog. If an attacker gains initial access via web shells or phishing, exploiting this vulnerability allows them to bypass endpoint security controls, dump credentials, and perform lateral movement across the enterprise network, posing a severe threat to business continuity.
Official Vendor Advisories & References
Win32k.sys in the kernel-mode drivers in Microsoft Windows Server 2003 SP2, Vista SP2, and Server 2008 SP2 allows local users to gain privileges via a crafted application, as exploited in the wild in April 2015, aka "Win32k Elevation of Privilege Vulnerability."
Frequently Asked SecOps Questions (CVE-2015-1701)
FAQQ1. How critical is CVE-2015-1701 and is it actively exploited in the wild?
CVE-2015-1701 is rated CVSS 7.8 (HIGH) with a 30-day EPSS exploitation probability of 55.9%. It is listed in the CISA Known Exploited Vulnerabilities (KEV) catalog, requiring immediate emergency remediation.
Q2. Which vendors and products are affected by CVE-2015-1701?
Primary impacted vendors include microsoft across windows_server_2003, windows_vista, windows_server_2008. Scope summary: Microsoft Windows Server 2003 SP2, Windows Vista SP2, and Windows Server 2008 SP2 running vulnerable win32k.sys drivers
Q3. What temporary mitigations or workarounds exist for CVE-2015-1701 before patching?
[Mitigation] Apply the official Microsoft MS15-051 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-2015-1701
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