Uncontrolled Memory Allocation in Windows and Windows Server - CVE-2026-40378
Published: July 17, 2026
Vulnerability identifier: #VU137959
CSH Severity: Medium
CVSS v4.0: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:U/U:Green
CVE-ID: CVE-2026-40378
CWE-ID: CWE-789
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vendor: Microsoft
Affected software:
Windows
Windows Server
Windows
Windows Server
Detailed vulnerability description
The vulnerability allows a remote attacker to cause a denial of service.
The vulnerability exists due to memory allocation with excessive size value in Windows Local Security Authority Subsystem Service (LSASS) when handling network requests. A remote attacker can send a specially crafted request to cause a denial of service.
How to mitigate CVE-2026-40378
Install security update from vendor's website.