CVE-2025-59257: Windows Local Session Manager (LSM) Denial of Service Vulnerability

Severity: medium (CVSS 6.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 1.5% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2025-10-14 · updated 2026-10-18
Weakness: CWE-1287

Description

Improper validation of specified type of input in Windows Local Session Manager (LSM) allows an authorized attacker to deny service over a network.

Affected products

Microsoft Windows 11: before 10.0.26100.6899 — fixed in 10.0.26100.6899
Microsoft Windows 11 25H2: before 10.0.26200.6899 — fixed in 10.0.26200.6899
Microsoft Windows Server 2022, 23H2 Edition (Server Core installation): before 10.0.25398.1913 — fixed in 10.0.25398.1913
Microsoft Windows Server 2025: through 10.0.26100.6899
Microsoft Windows 11: from 10.0.26100.0 before 10.0.26100.6899 — fixed in 10.0.26100.6899
Microsoft Windows 11 25H2: from 10.0.26200.0 before 10.0.26200.6899 — fixed in 10.0.26200.6899
Microsoft Windows Server 2022, 23H2 Edition (Server Core installation): from 10.0.25398.0 before 10.0.25398.1913 — fixed in 10.0.25398.1913
Microsoft Windows Server 2025: from 10.0.26100.0 before 10.0.26100.6899 — fixed in 10.0.26100.6899

How to fix

Upgrade to a fixed version: Microsoft Windows 11 10.0.26100.6899; Microsoft Windows 11 25H2 10.0.26200.6899; Microsoft Windows Server 2022, 23H2 Edition (Server Core installation) 10.0.25398.1913; Microsoft Windows 11 10.0.26100.6899; Microsoft Windows 11 25H2 10.0.26200.6899; Microsoft Windows Server 2022, 23H2 Edition (Server Core installation) 10.0.25398.1913; Microsoft Windows Server 2025 10.0.26100.6899. Check the vendor advisory for mitigations.

References

https://msrc.microsoft.com/update-guide/vulnerability/CVE-2025-59257

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