Microsoft Windows Win32k Kernel-Mode Driver Memory Corruption Privilege Escalation (CVE-2015-2546, MS15-097)
Executive & SecOps Summary
SECOPS ASSESSMENTLegacy Windows operating systems including Windows Vista SP2, 7 SP1, 8, 8.1, 10, and Windows Server 2008/2012
Local attackers can execute a crafted application to gain elevated SYSTEM privileges and fully compromise the host
Apply the official Microsoft security update (MS15-097) immediately or upgrade to a supported OS version
Affected Products & Version Scope
Remediation & Live Workaround Commands
PATCH & WORKAROUND1. Official Patch & Version Upgrade Commands
Deploy the official MS15-097 security update to remediate this vulnerability. For automated deployment via PowerShell, use the following commands:
# Install the specific KB update associated with MS15-097
Get-WUInstall -KBArticleID KB3087038 -AcceptAll -AutoReboot2. Temporary Workaround & Hardening Configuration
Because this is a kernel-level vulnerability, there are no viable workarounds other than restricting local execution privileges. Implement AppLocker to prevent unauthorized executable files from running on vulnerable hosts.
# Enable and start the Application Identity service for AppLocker enforcement
Set-Service -Name 'AppIDSvc' -StartupType Automatic
Start-Service -Name 'AppIDSvc'3. Log Audit & IoC Verification Commands
Verify the patch level of the system by checking the file version of win32k.sys using the following PowerShell script:
# Check 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)"
} else {
Write-Warning "win32k.sys was not found in the default path."
}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 is a Use-After-Free (UAF) memory corruption flaw residing in the Windows kernel-mode driver win32k.sys. It occurs because the driver fails to properly manage objects in memory when handling specific window messages or callback functions, allowing a dangling pointer to be dereferenced after the associated memory has been freed.
2. Exploitation Mechanics & Attack Scenario
A local attacker with low-privilege access executes a specially crafted user-mode application that creates specific window or menu objects. By hijacking the window message loop or utilizing user-mode callbacks, the attacker forces the kernel to free the target object while retaining a reference to it. The attacker then reclaims the freed memory space with controlled payload data. When the kernel subsequently dereferences the stale pointer, it executes the attacker's shellcode with kernel-level (SYSTEM) privileges.
3. Infrastructure & Business Impact
As a CISA KEV-listed vulnerability, CVE-2015-2546 has been actively exploited in the wild by advanced persistent threat (APT) actors and malware campaigns. Successful exploitation bypasses all local security boundaries, allowing attackers to install persistent backdoors, disable endpoint security controls, harvest credentials, and perform 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, Windows 8.1, Windows Server 2012 Gold and R2, Windows RT Gold and 8.1, and Windows 10 allows local users to gain privileges via a crafted application, aka "Win32k Memory Corruption Elevation of Privilege Vulnerability," a different vulnerability than CVE-2015-2511, CVE-2015-2517, and CVE-2015-2518.
Frequently Asked SecOps Questions (CVE-2015-2546)
FAQQ1. How critical is CVE-2015-2546 and is it actively exploited in the wild?
CVE-2015-2546 is rated CVSS 8.2 (HIGH) with a 30-day EPSS exploitation probability of 10.1%. It is listed in the CISA Known Exploited Vulnerabilities (KEV) catalog, requiring immediate emergency remediation.
Q2. Which vendors and products are affected by CVE-2015-2546?
Primary impacted vendors include microsoft across windows, windows_server. Scope summary: Windows Vista SP2, Windows 7 SP1, Windows 8/8.1, Windows 10, and Windows Server 2008 SP2/R2 SP1, Windows Server 2012 Gold/R2
Q3. What temporary mitigations or workarounds exist for CVE-2015-2546 before patching?
[Mitigation] Apply the official Microsoft security update (MS15-097) immediately or upgrade to a supported OS version 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-2015-2546
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