CVE-2018-8639 Microsoft Windows Win32k Improper Resource Shutdown or Release Vulnerability
Microsoft Windows Win32k contains an improper resource shutdown or release vulnerability that allows for local, authenticated privilege escalation. An attacker who successfully exploited this vulnerability could run arbitrary code in kernel mode.
From the CISA KEV catalogue version 2026.11.06, with Cybergen analysis. Updated 6 Nov 2026.
Should You Worry?
- CISA confirmed exploitation in the wild and added it to the Known Exploited Vulnerabilities catalogue on 3 Mar 2025.
- CISA lists it as known to be used in ransomware campaigns.
- Rated High severity (CVSS 8.4, scored by CISA).
- It has been in the catalogue for 613 days. Systems still unpatched now have almost certainly been scanned for it.
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. This CVE ID is unique from CVE-2018-8641.
Affected Versions
| Product | Versions |
|---|---|
| Microsoft Windows 7 | 32-bit Systems Service Pack 1 x64-based Systems Service Pack 1 |
| Microsoft Windows Server 2012 R2 | (Server Core installation) |
| Microsoft Windows RT 8.1 | Windows RT 8.1 |
| Microsoft Windows Server 2008 | 32-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.
What To Do Now
- 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
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
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
Prove it is fixed
Rescan or test the system after patching. Upgrades that fail silently and forgotten secondary instances are common.
Penetration Testing
The Compliance Clock
General guidance, not legal advice. Your obligations depend on your sector, scope and jurisdiction.
Not Sure If You Are Exposed?
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