CVE-2026-20921 Windows SMB Server Elevation of Privilege Vulnerability
An authorized attacker can elevate privileges over the network by exploiting a race condition in the Windows SMB Server.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-20921?
CVE-2026-20921 is a high-severity vulnerability in Microsoft Windows 10 1607, published on 13 Jan 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Official description
Concurrent execution using shared resource with improper synchronization ('race condition') in Windows SMB Server allows an authorized attacker to elevate privileges over a network.
Weakness: CWE-362
Which versions are affected by CVE-2026-20921?
It affects 14 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 8 more.
How do I fix CVE-2026-20921?
No fix has been published for CVE-2026-20921 yet. Limit exposure of the affected software until one is available.
Is CVE-2026-20921 being exploited?
There is no known exploitation of CVE-2026-20921 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-rj95-xj64-7m2x.