CVE-2026-20856

HIGH

8.1

Description

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

CVE Details

CVSS v3.1 Score8.1

SeverityHIGH

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

Attack VectorNETWORK

ComplexityHIGH

Privileges RequiredNONE

User InteractionNONE

Published1/13/2026

Last Modified1/15/2026

Sourcenvd

Honeypot Sightings0

Affected Products

microsoft:windows_10_1607microsoft:windows_10_1809microsoft:windows_10_21h2microsoft:windows_10_22h2microsoft:windows_11_23h2microsoft:windows_11_24h2microsoft:windows_11_25h2microsoft:windows_server_2012microsoft:windows_server_2016microsoft:windows_server_2019microsoft:windows_server_2022microsoft:windows_server_2022_23h2microsoft:windows_server_2025

Weaknesses (CWE)

CWE-20

References

https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-20856(secure@microsoft.com)

IOC Correlations

No correlations recorded

This product uses data from the NVD API but is not endorsed or certified by the NVD.