CVE-2026-40405 Windows TCP/IP Denial of Service Vulnerability
An unauthorized attacker can cause a denial of service in Windows TCP/IP due to a null pointer dereference.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-40405?
CVE-2026-40405 is a high-severity vulnerability in Microsoft Windows 11 24h2, published on 12 May 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
Null pointer dereference in Windows TCP/IP allows an unauthorized attacker to deny service over a network.
Weakness: CWE-476
Which versions are affected by CVE-2026-40405?
It affects 4 products.
Products include Microsoft Windows 11 24h2, Microsoft Windows 11 25h2, Microsoft Windows 11 26h1, Microsoft Windows Server 2025.
How do I fix CVE-2026-40405?
No fix has been published for CVE-2026-40405 yet. Limit exposure of the affected software until one is available.
Is CVE-2026-40405 being exploited?
There is no known exploitation of CVE-2026-40405 in the wild and no public exploit code.
Other vulnerabilities in Microsoft Windows 11 24h2
- CVE-2025-60710 Microsoft Windows Link Following
- CVE-2026-54990 Remote Desktop Client Remote Code Execution Vulnerability
- CVE-2025-50165 Windows Graphics Component Remote Code Execution Vulnerability
- CVE-2025-21311 Windows NTLM V1 Elevation of Privilege Vulnerability
- CVE-2026-108463 Windows SmartScreen Security Feature Bypass Vulnerability
Sources
Also known as GHSA-mj3g-9j9x-c556.