CVE-2026-20842 Microsoft DWM Core Library Elevation of Privilege Vulnerability
An authorized local attacker can exploit a use-after-free flaw in the Windows DWM Core Library 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-2026-20842?
CVE-2026-20842 is a high-severity use after free vulnerability in Microsoft Windows 10 21h2, published on 13 Jan 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
Use after free in Windows DWM allows an authorized attacker to elevate privileges locally.
Weakness: CWE-416
Which versions are affected by CVE-2026-20842?
It affects 8 products.
Products include Microsoft Windows 10 21h2, Microsoft Windows 10 22h2, Microsoft Windows 11 23h2, Microsoft Windows 11 24h2, Microsoft Windows 11 25h2, Microsoft Windows Server 2022 and 2 more.
How do I fix CVE-2026-20842?
No fix has been published for CVE-2026-20842 yet. Limit exposure of the affected software until one is available.
Upgrade to the fixed version. These bugs are found with fuzzing and sanitisers and avoided by memory-safe languages. More about Use after free.
Is CVE-2026-20842 being exploited?
There is no known exploitation of CVE-2026-20842 in the wild and no public exploit code.
Other vulnerabilities in Microsoft Windows 10 21h2
- CVE-2025-21333 Microsoft Windows Hyper-V NT Kernel Integration VSP Heap-based Buffer Overflow
- CVE-2025-21334 Microsoft Windows Hyper-V NT Kernel Integration VSP Use-After-Free
- CVE-2025-21335 Microsoft Windows Hyper-V NT Kernel Integration VSP Use-After-Free
- CVE-2026-42904 Windows TCP/IP Elevation of Privilege Vulnerability
- CVE-2026-105733 Windows Hyper-V Remote Code Execution Vulnerability
Sources
Also known as GHSA-4f9p-rpf6-78qv.