Jul 2026: Windows Local Security Authority Subsystem Service (LSASS) Denial of Service Vulnerability
CVE-2026-40378 Published on July 14, 2026

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.

Vendor Advisory NVD

Weakness Type

What is a Stack Exhaustion Vulnerability?

The product allocates memory based on an untrusted, large size value, but it does not ensure that the size is within expected limits, allowing arbitrary amounts of memory to be allocated.

CVE-2026-40378 has been classified to as a Stack Exhaustion vulnerability or weakness.

Products Associated with CVE-2026-40378

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Microsoft Windows 10

Microsoft Windows Server 2019

Microsoft Windows Server 2022

Microsoft Windows Server 2025

Microsoft Windows 11 25h2

Microsoft Windows 11 23h2

Microsoft Windows 11 24h2

Microsoft Windows 11 26h1

Microsoft Windows Server 2016

Microsoft Windows Server 2012

Microsoft Windows Server 2012 R2

Affected Versions

Microsoft Windows 10 Version 1607:

Version 10.0.14393.0 and below 10.0.14393.9339 is affected.

Microsoft Windows 10 Version 1809:

Version 10.0.17763.0 and below 10.0.17763.9020 is affected.

Microsoft Windows 10 Version 21H2:

Version 10.0.19044.0 and below 10.0.19044.7548 is affected.

Microsoft Windows 10 Version 22H2:

Version 10.0.19045.0 and below 10.0.19045.7548 is affected.

Microsoft Windows 11 version 23H2:

Version 10.0.22631.0 and below 10.0.22631.7376 is affected.

Microsoft Windows 11 Version 23H2:

Version 10.0.22631.0 and below 10.0.22631.7376 is affected.

Microsoft Windows 11 Version 24H2:

Version 10.0.26100.0 and below 10.0.26100.8875 is affected.

Microsoft Windows 11 Version 25H2:

Version 10.0.26200.0 and below 10.0.26200.8875 is affected.

Microsoft Windows 11 version 26H1:

Version 10.0.28000.0 and below 10.0.28000.2525 is affected.

Microsoft Windows Server 2012:

Version 6.2.9200.0 and below 6.2.9200.26226 is affected.

Microsoft Windows Server 2012 (Server Core installation):

Version 6.2.9200.0 and below 6.2.9200.26226 is affected.

Microsoft Windows Server 2012 R2:

Version 6.3.9600.0 and below 6.3.9600.23291 is affected.

Microsoft Windows Server 2012 R2 (Server Core installation):

Version 6.3.9600.0 and below 6.3.9600.23291 is affected.

Microsoft Windows Server 2016:

Version 10.0.14393.0 and below 10.0.14393.9339 is affected.

Microsoft Windows Server 2016 (Server Core installation):

Version 10.0.14393.0 and below 10.0.14393.9339 is affected.

Microsoft Windows Server 2019:

Version 10.0.17763.0 and below 10.0.17763.9020 is affected.

Microsoft Windows Server 2019 (Server Core installation):

Version 10.0.17763.0 and below 10.0.17763.9020 is affected.

Microsoft Windows Server 2022:

Version 10.0.20348.0 and below 10.0.20348.5386 is affected.

Microsoft Windows Server 2025:

Version 10.0.26100.0 and below 10.0.26100.33158 is affected.

Microsoft Windows Server 2025 (Server Core installation):

Version 10.0.26100.0 and below 10.0.26100.33158 is affected.

Exploit Probability

EPSS

0.82%

Percentile

53.37%