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Actively exploitedKnown ransomware use

CVE-2018-8453 Microsoft Win32k Privilege Escalation Vulnerability

Microsoft Windows Win32k contains a vulnerability that allows an attacker to escalate 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 21 Jan 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 1,750 days. Systems still unpatched now have almost certainly been scanned for it.
The Vulnerability

What It Is

An elevation of privilege vulnerability exists in Windows when the Win32k component fails to properly handle objects in memory, aka "Win32k Elevation of Privilege Vulnerability." This affects Windows 7, Windows Server 2012 R2, Windows RT 8.1, Windows Server 2008, Windows Server 2019, Windows Server 2012, Windows 8.1, Windows Server 2016, Windows Server 2008 R2, Windows 10, Windows 10 Servers.

Affected Versions

ProductVersions
Microsoft Windows 732-bit Systems Service Pack 1
x64-based Systems Service Pack 1
Microsoft Windows Server 2012 R2(Server Core installation)
Microsoft Windows RT 8.1Windows RT 8.1
Microsoft Windows Server 200832-bit Systems Service Pack 2
32-bit Systems Service Pack 2 (Server Core installation)
Itanium-Based Systems Service Pack 2
x64-based Systems Service Pack 2
x64-based Systems Service Pack 2 (Server Core installation)
Microsoft Windows Server 2019(Server Core installation)
Microsoft Windows Server 2012(Server Core installation)

From the public CVE record, as supplied by the vendor. Always confirm against the vendor advisory.

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 21 Jul 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-2018-8453
  3. CVE record: CVE-2018-8453
  4. FIRST EPSS
  5. securitytracker.com/id/1041828
  6. securelist.com/cve-2018-8453-used-in-targeted-attack
  7. portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2018-8453
  8. securityfocus.com/bid/105467
  9. packetstormsecurity.com/files/153669/Microsoft-Windows-NtUserSetWindowFNID-Win32k-User-Callback.html