CVE-2026-20856

HIGH

Windows Server Update Service - Code Injection

Title source: llm
STIX 2.1

Description

Improper input validation in Windows Server Update Service allows an unauthorized attacker to execute code over a network.

References (1)

Core 1
Core References

Scores

CVSS v3 8.1
EPSS 0.0018
EPSS Percentile 39.7%
Attack Vector NETWORK
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H

CISA SSVC

Vulnrichment
Exploitation none
Automatable no
Technical Impact total

Details

CWE
CWE-20
Status published
Products (34)
Microsoft/Windows 10 Version 1607 10.0.14393.0 - 10.0.14393.8783
Microsoft/Windows 10 Version 1809 10.0.17763.0 - 10.0.17763.8276
Microsoft/Windows 10 Version 21H2 10.0.19044.0 - 10.0.19044.6809
Microsoft/Windows 10 Version 22H2 10.0.19045.0 - 10.0.19045.6809
Microsoft/Windows 11 version 22H3 10.0.22631.0 - 10.0.22631.6491
Microsoft/Windows 11 Version 23H2 10.0.22631.0 - 10.0.22631.6491
Microsoft/Windows 11 Version 24H2 10.0.26100.0 - 10.0.26100.7623
Microsoft/Windows 11 Version 25H2 10.0.26200.0 - 10.0.26200.7623
Microsoft/Windows Server 2012 6.2.9200.0 - 6.2.9200.25868
Microsoft/Windows Server 2012 (Server Core installation) 6.2.9200.0 - 6.2.9200.25868
... and 24 more
Published Jan 13, 2026
Tracked Since Feb 18, 2026