CVE-2024-21338 Microsoft Windows Kernel Exposed IOCTL with Insufficient Access Control Vulnerability
Microsoft Windows Kernel contains an exposed IOCTL with insufficient access control vulnerability within the IOCTL (input and output control) dispatcher in appid.sys that allows a local attacker to achieve privilege escalation.
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 4 Mar 2024.
- CISA lists it as known to be used in ransomware campaigns.
- Rated High severity (CVSS 7.8, scored by Vendor).
- It has been in the catalogue for 977 days. Systems still unpatched now have almost certainly been scanned for it.
What It Is
Windows Kernel Elevation of Privilege Vulnerability
Affected Versions
| Product | Versions |
|---|---|
| Microsoft Windows 10 Version 1809 | 10.0.17763.0 to before 10.0.17763.5458 |
| Microsoft Windows 10 Version 1809 | 10.0.0 to before 10.0.17763.5458 |
| Microsoft Windows 10 Version 21H2 | 10.0.19043.0 to before 10.0.19044.4046 |
| Microsoft Windows 10 Version 22H2 | 10.0.19045.0 to before 10.0.19045.4046 |
| Microsoft Windows 11 version 21H2 | 10.0.0 to before 10.0.22000.2777 |
| Microsoft Windows 11 version 22H2 | 10.0.22621.0 to before 10.0.22621.3155 |
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 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.
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