Improper Input Validation in Windows Server Update Service Enables Remote Code Execution

Publication date: 2026-01-13

Last updated on: 2026-01-13

Assigner: Microsoft Corporation

Description

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

CVSS Scores

EPSS Scores

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Meta Information

Published

2026-01-13

Last Modified

2026-01-13

Generated

2026-07-06

AI Q&A

2026-01-14

EPSS Evaluated

2026-07-05

NVD

CVE-2026-20856

Affected Vendors & Products

Vendor	Product	Version / Range
microsoft	windows_server_update_service	*

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-20	The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly.

Attack-Flow Graph

Executive Summary

This vulnerability is due to improper input validation in Windows Server Update Service, which allows an unauthorized attacker to execute code remotely over a network.

Impact Analysis

An attacker exploiting this vulnerability can execute arbitrary code on the affected system remotely, potentially leading to full compromise of confidentiality, integrity, and availability of the system.

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