CVE-2026-20854

Windows Local Security Authority Subsystem Service (LSASS) Remote Code Execution Vulnerability

CVE-2026-20854 is fixed in 6 products on 1 platform, first by KB5074109, released January 13, 2026. It is not reported as exploited. Patch Radar priority: Urgent.

Urgent

CVSS

7.5

Critical

Exploitation

None reported

Exploitation Less Likely

CISA KEV

Not listed

Not in the Known Exploited Vulnerabilities catalog

EPSS

0.0108

65th percentile

<p>Use after free in Windows Local Security Authority Subsystem Service (LSASS) allows an authorized attacker to execute code over a network.</p>

Where it's fixed

Product	Fixed in	Fix	Released
Microsoft
Windows 11 Version 24H2 for ARM64-based Systems		KB5074109	Jan 13, 2026
Windows 11 Version 24H2 for x64-based Systems		KB5074109	Jan 13, 2026
Windows 11 Version 25H2 for ARM64-based Systems		KB5074109	Jan 13, 2026
Windows 11 Version 25H2 for x64-based Systems		KB5074109	Jan 13, 2026
Windows Server 2025	26100.32230	KB5073379	Jan 13, 2026
Windows Server 2025 (Server Core installation)	26100.32230	KB5073379	Jan 13, 2026

Details

Published
January 13, 2026
Weakness
Use After Free
Vendor advisory
https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-20854

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