CVE-2026-40378

Published: Jul 14, 2026Modified: Jul 22, 2026

7.5

Vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Exploitability: 3.9 / Impact: 3.6

Source: secure@microsoft.com (Secondary)

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.

Affected (24)

Products: Microsoft: Windows 10 1607, Windows 10 1809, Windows 10 21h2, Windows 10 22h2, Windows 11 23h2, Windows 11 24h2, Windows 11 25h2, Windows 11 26h1, Windows Server 2012, Windows Server 2016, Windows Server 2019, Windows Server 2022, Windows Server 2025

13 products

Configuration A

24 vulnerable

Vulnerable Software	Affected Versions
Microsoft Windows 10 1607	Before 10.0.14393.9339
Microsoft Windows 10 1607	Before 10.0.14393.9339
Microsoft Windows 10 1809	Before 10.0.17763.9020
Microsoft Windows 10 1809	Before 10.0.17763.9020
Microsoft Windows 10 21h2	Before 10.0.19044.7548
Microsoft Windows 10 21h2	Before 10.0.19044.7548
Microsoft Windows 10 21h2	Before 10.0.19044.7548
Microsoft Windows 10 22h2	Before 10.0.19045.7548
Microsoft Windows 10 22h2	Before 10.0.19045.7548
Microsoft Windows 10 22h2	Before 10.0.19045.7548
Microsoft Windows 11 23h2	Before 10.0.22631.7376
Microsoft Windows 11 23h2	Before 10.0.22631.7376
Microsoft Windows 11 24h2	Before 10.0.26100.8875
Microsoft Windows 11 24h2	Before 10.0.26100.8875
Microsoft Windows 11 25h2	Before 10.0.26200.8875
Microsoft Windows 11 25h2	Before 10.0.26200.8875
Microsoft Windows 11 26h1	Before 10.0.28000.2269
Microsoft Windows 11 26h1	Before 10.0.28000.2269
Microsoft Windows Server 2012	All versions
Microsoft Windows Server 2012	Version r2
Microsoft Windows Server 2016	Before 10.0.14393.9339
Microsoft Windows Server 2019	Before 10.0.17763.9020
Microsoft Windows Server 2022	Before 10.0.20348.5386
Microsoft Windows Server 2025	Before 10.0.26100.33158

Related CWEs

CWE-789

Memory Allocation with Excessive Size Value

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.

References (1)

https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-40378

Source: secure@microsoft.com

Vendor Advisory

Timeline

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