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Actively exploited

CVE-2011-3402 Microsoft Windows Remote Code Execution Vulnerability

Microsoft Windows Kernel contains an unspecified vulnerability in the TrueType font parsing engine in win32k.sys in the kernel-mode drivers that allows remote attackers to execute arbitrary code via crafted font data in a Word document or web page.

From the CISA KEV catalogue version 2026.11.06, with Cybergen analysis. Updated 6 Nov 2026.

Our Assessment

Should You Worry?

Patch urgentlyCybergen assessment
  • CISA confirmed exploitation in the wild and added it to the Known Exploited Vulnerabilities catalogue on 6 Oct 2025.
  • Rated High severity (CVSS 8.8, scored by CISA).
  • It has been in the catalogue for 396 days. Systems still unpatched now have almost certainly been scanned for it.
The Vulnerability

What It Is

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."

From Watch to Action

What To Do Now

  1. 1

    Find it

    Search your asset inventory and external attack surface for Microsoft Windows. Include cloud images, appliances and anything a supplier runs for you.

    Attack Surface Management
  2. 2

    Fix it

    Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.

    Vulnerability Management
  3. 3

    Hunt for compromise

    If an affected system was reachable before you patched, assume it may have been hit. Check logs, new accounts, web shells and outbound connections from the date of exposure.

    Incident Response
  4. 4

    Prove it is fixed

    Rescan or test the system after patching. Upgrades that fail silently and forgotten secondary instances are common.

    Penetration Testing

Vendor Advisories

Regulation

The Compliance Clock

Cyber EssentialsRated high, so if it affects devices in your Cyber Essentials scope, the update must be installed within 14 days of the vendor releasing it.NIS2If exploitation causes a significant incident, essential and important entities owe their CSIRT an early warning within 24 hours and a notification within 72 hours.DORAFinancial entities must classify ICT incidents and send an initial notification for a major incident within strict deadlines, with exploited flaws a common cause.US federal (BOD 22-01)Federal civilian agencies had until 27 Oct 2025 to remediate. A sensible benchmark for everyone else.

General guidance, not legal advice. Your obligations depend on your sector, scope and jurisdiction.

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Evidence

Sources

  1. CISA Known Exploited Vulnerabilities catalogue
  2. NVD: CVE-2011-3402
  3. CVE record: CVE-2011-3402
  4. FIRST EPSS
  5. docs.microsoft.com/en-us/security-updates/securitybulletins/2011/ms11-087
  6. secunia.com/advisories/49121
  7. oval.cisecurity.org/repository/search/definition/oval%3Aorg.mitre.oval%3Adef%3A15645
  8. us-cert.gov/cas/techalerts/TA12-164A.html
  9. blogs.mcafee.com/mcafee-labs/the-day-of-the-golden-jackal-%E2%80%93-further-tales-of-the-stuxnet-fil
  10. securitytracker.com/id?1027039
  11. secunia.com/advisories/49122
  12. symantec.com/content/en/us/enterprise/media/security_response/whitepapers/w32_duqu_the_precursor_to_