High MSRC-CVE-2026-40378 1 CVE

Windows Local Security Authority Subsystem Service (LSASS) Denial of Service Vulnerability

Published Jul 14, 2026 · Updated Jul 14, 2026

Vendor: Microsoft

Summary

Impact: Denial of Service. Microsoft rating: Important. Not known to be exploited — Exploitation Less Likely. Customer action: Required.

Details

Security updates
10.0.17763.9020 — https://support.microsoft.com/help/5099538
10.0.20348.5386 — https://support.microsoft.com/help/5099540
10.0.19044.7548 — https://support.microsoft.com/help/5099539
10.0.26100.33158 — https://support.microsoft.com/help/5099536
10.0.26200.8875 — https://support.microsoft.com/help/5101650
10.0.22631.7376 — https://support.microsoft.com/help/5099414
10.0.28000.2525 — https://support.microsoft.com/help/5101649
10.0.28000.2269 — https://support.microsoft.com/help/5095051
10.0.14393.9339 — https://support.microsoft.com/help/5099535
6.2.9200.26226 — https://support.microsoft.com/help/5099445
6.3.9600.23291 — https://support.microsoft.com/help/5099444

Vulnerabilities 1

High 7.5

CVE-2026-40378

Windows Local Security Authority Subsystem Service (LSASS) Denial of Service Vulnerability

Memory allocation with excessive size value in Windows Local Security Authority Subsystem Service (LSASS) allows an unauthorized attacker to deny service over a network.

Microsoft Windows Server 2019 Windows Server 2019 (Server Core installation) Windows 10 Version 1809 Windows

Jul 14, 2026

Revision history

2026-07-14 #1
Information published.

References

CVE-2026-40378 Windows Local Security Authority Subsystem Service (LSASS) Denial of Service Vulnerability - HTML
https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-40378
Microsoft Exploitability Index
https://www.microsoft.com/en-us/msrc/exploitability-index?rtc=1
Microsoft Support Lifecycle
https://support.microsoft.com/lifecycle
Common Vulnerability Scoring System
https://www.first.org/cvss