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HIGH · 7.5

CVE-2026-40378

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

Vulnerability Description

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

CVSS Score

7.5

HIGH

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
NONE
Integrity
NONE
Availability
HIGH

Affected Products

VendorProductVersions
MicrosoftWindows 10 1607< 10.0.14393.9339
MicrosoftWindows 10 1809< 10.0.17763.9020
MicrosoftWindows 10 21H2< 10.0.19044.7548
MicrosoftWindows 10 22H2< 10.0.19045.7548
MicrosoftWindows 11 23H2< 10.0.22631.7376
MicrosoftWindows 11 24H2< 10.0.26100.8875
MicrosoftWindows 11 25H2< 10.0.26200.8875
MicrosoftWindows 11 26H1< 10.0.28000.2269
MicrosoftWindows Server 2012-
MicrosoftWindows Server 2016< 10.0.14393.9339
MicrosoftWindows Server 2019< 10.0.17763.9020
MicrosoftWindows Server 2022< 10.0.20348.5386
MicrosoftWindows Server 2025< 10.0.26100.33158

Related Weaknesses (CWE)

CWE-789

References

FAQ

What is CVE-2026-40378?

CVE-2026-40378 is a vulnerability with a CVSS score of 7.5 (HIGH). Memory allocation with excessive size value in Windows Local Security Authority Subsystem Service (LSASS) allows an unauthorized attacker to deny service over a network.

How severe is CVE-2026-40378?

CVE-2026-40378 has been rated HIGH with a CVSS base score of 7.5/10. Review the CVSS metrics above for detailed severity breakdown.

Is there a patch for CVE-2026-40378?

Check the references section above for vendor advisories and patch information. Affected products include: Microsoft Windows 10 1607, Microsoft Windows 10 1809, Microsoft Windows 10 21H2, Microsoft Windows 10 22H2, Microsoft Windows 11 23H2.