Microsoft Windows win32k.sys TrueType Font Parsing Engine Remote Code Execution Vulnerability (CVE-2011-3402, Duqu Exploited)
Executive & SecOps Summary
SECOPS ASSESSMENTWindows XP, Vista, 7, and Windows Server 2003, 2008 kernel-mode drivers (win32k.sys)
Remote code execution (RCE) with kernel-level privileges via crafted TrueType font data in Word documents or web pages
Apply official MS11-087 security patches or implement the T2EMBED.DLL registry/ACL workaround
Affected Products & Version Scope
Remediation & Live Workaround Commands
PATCH & WORKAROUND1. Official Patch & Version Upgrade Commands
Apply the official Microsoft security update (MS11-087). For legacy systems, you can use the following PowerShell commands to check and install the required update.
# Install and search for the specific KB update using PSWindowsUpdate
Install-Module PSWindowsUpdate -Force -Verbose
Get-WindowsUpdate -KBArticleID KB2639658 -Install -AcceptAll -AutoReboot2. Temporary Workaround & Hardening Configuration
If patching is not immediately feasible, restrict access to T2EMBED.DLL to mitigate the attack vector.
:: Restrict access to T2EMBED.DLL using icacls (Run as Administrator)
takeown /f %windir%\system32 2embed.dll
icacls %windir%\system32 2embed.dll /deny everyone:(F)3. Log Audit & IoC Verification Commands
Use the following PowerShell script to verify the file version of win32k.sys to determine if the system remains vulnerable.
# Check the file version of win32k.sys
$sysPath = '$env:windir\system32\win32k.sys'
if (Test-Path $sysPath) {
$fileVersion = (Get-Item $sysPath).VersionInfo.FileVersion
Write-Host 'Current win32k.sys Version:' $fileVersion
}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 memory corruption issue within the TrueType font (TTF) parsing engine in the Windows kernel-mode driver win32k.sys. It is caused by insufficient validation of user-supplied font input when the operating system parses font files, allowing an attacker to corrupt kernel memory and hijack the execution flow.
2. Exploitation Mechanics & Attack Scenario
An attacker crafts a malicious TrueType font and embeds it inside a Microsoft Word document (.doc) or a web page. When a user opens the document or visits the web page using a vulnerable browser like Internet Explorer, the system calls the win32k.sys engine to render the font. This triggers the parsing flaw, executing arbitrary code with SYSTEM privileges. This vulnerability was actively exploited in the wild as a zero-day by the 'Duqu' APT malware.
3. Infrastructure & Business Impact
Although the attack requires user interaction (opening a document or visiting a site), successful exploitation grants the attacker complete control over the target system. Because the code executes in kernel mode, it bypasses standard User Account Control (UAC) and application sandboxes, leading to lateral movement and critical data exfiltration within enterprise networks.
Official Vendor Advisories & References
Unspecified vulnerability in the TrueType font parsing engine in win32k.sys in the kernel-mode drivers in Microsoft Windows XP SP2 and SP3, Windows Server 2003 SP2, Windows Vista SP2, Windows Server 2008 SP2, R2, and R2 SP1, and Windows 7 Gold and SP1 allows remote attackers to execute arbitrary code via crafted font data in a Word document or web page, as exploited in the wild in November 2011 by Duqu, aka "TrueType Font Parsing Vulnerability."
Frequently Asked SecOps Questions (CVE-2011-3402)
FAQQ1. How critical is CVE-2011-3402 and is it actively exploited in the wild?
CVE-2011-3402 is rated CVSS 8.8 (HIGH) with a 30-day EPSS exploitation probability of 78.1%. It is listed in the CISA Known Exploited Vulnerabilities (KEV) catalog, requiring immediate emergency remediation.
Q2. Which vendors and products are affected by CVE-2011-3402?
Primary impacted vendors include microsoft across windows, windows_server. Scope summary: Windows XP SP2/SP3, Windows Server 2003 SP2, Windows Vista SP2, Windows Server 2008 SP2/R2, Windows 7 Gold/SP1
Q3. What temporary mitigations or workarounds exist for CVE-2011-3402 before patching?
[Mitigation] Apply official MS11-087 security patches or implement the T2EMBED.DLL registry/ACL workaround 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-2011-3402
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