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Actively exploitedKnown ransomware use

CVE-2015-1701 Microsoft Win32k Privilege Escalation Vulnerability

An unspecified vulnerability exists in the Win32k.sys kernel-mode driver in Microsoft Windows Server that allows a local attacker to execute arbitrary code with elevated privileges.

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

Our Assessment

Should You Worry?

Patch nowCybergen assessment
  • CISA confirmed exploitation in the wild and added it to the Known Exploited Vulnerabilities catalogue on 3 Mar 2022.
  • CISA lists it as known to be used in ransomware campaigns.
  • Rated High severity (CVSS 7.8, scored by CISA).
  • It has been in the catalogue for 1,709 days. Systems still unpatched now have almost certainly been scanned for it.
The Vulnerability

What It Is

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."

From Watch to Action

What To Do Now

  1. 1

    Find it

    Search your asset inventory and external attack surface for Microsoft Win32k. Include cloud images, appliances and anything a supplier runs for you.

    Attack Surface Management
  2. 2

    Fix it

    Apply updates per vendor instructions.

    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 24 Mar 2022 to remediate. A sensible benchmark for everyone else.

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

Stay Ahead

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Evidence

Sources

  1. CISA Known Exploited Vulnerabilities catalogue
  2. NVD: CVE-2015-1701
  3. CVE record: CVE-2015-1701
  4. FIRST EPSS
  5. twitter.com/symantec/statuses/590208710527549440
  6. exploit-db.com/exploits/37049/
  7. securityfocus.com/bid/74245
  8. docs.microsoft.com/en-us/security-updates/securitybulletins/2015/ms15-051
  9. exploit-db.com/exploits/37367/
  10. fireeye.com/blog/threat-research/2015/04/probable_apt28_useo.html
  11. securitytracker.com/id/1032155
  12. seclists.org/fulldisclosure/2020/May/34