CVE-2026-21239 Windows Kernel Elevation of Privilege Vulnerability
A heap-based buffer overflow in the Windows Kernel allows an authorized local attacker to elevate privileges.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-21239?
CVE-2026-21239 is a high-severity memory corruption vulnerability in Microsoft Windows 10 1607, published on 10 Feb 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
Heap-based buffer overflow in Windows Kernel allows an authorized attacker to elevate privileges locally.
Which versions are affected by CVE-2026-21239?
It affects 13 products.
Products include Microsoft Windows 10 1607, Microsoft Windows 10 1809, Microsoft Windows 10 21h2, Microsoft Windows 10 22h2, Microsoft Windows 11 23h2, Microsoft Windows 11 24h2 and 7 more.
How do I fix CVE-2026-21239?
No fix has been published for CVE-2026-21239 yet. Limit exposure of the affected software until one is available.
Upgrade to the fixed version. Memory-safe languages, compiler hardening and fuzzing prevent most new cases. More about Memory corruption.
Is CVE-2026-21239 being exploited?
There is no known exploitation of CVE-2026-21239 in the wild and no public exploit code.
Other vulnerabilities in Microsoft Windows 10 1607
- CVE-2026-33824 Microsoft Internet Key Exchange (IKE) Service Extensions Double Free
- CVE-2026-21510 Microsoft Windows Shell Protection Mechanism Failure
- CVE-2026-21513 Microsoft MSHTML Framework Protection Mechanism Failure
- CVE-2023-32049 Microsoft Windows Defender SmartScreen Security Feature Bypass
- CVE-2023-29360 Microsoft Streaming Service Untrusted Pointer Dereference
Sources
Also known as GHSA-5cch-r4ff-mh3m.