Remote Code Execution Vulnerability in Windows Server Update Service by Microsoft
CVE-2026-20856

8.1HIGH

Key Information:

Vendor

Microsoft
Status
Windows 10 Version 1809
Windows Server 2019
Windows Server 2019 (server Core Installation)
Windows Server 2022
Vendor
CVE Published:
13 January 2026

What is CVE-2026-20856?

An improper input validation vulnerability exists in the Windows Server Update Service, allowing unauthorized attackers to execute arbitrary code over a network. This flaw, if exploited, could enable an attacker to take control of affected systems, potentially leading to data breaches or unauthorized access to sensitive information. Organizations are advised to apply the latest security patches to mitigate this risk and protect their infrastructure.

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Affected Version(s)

Windows 10 Version 1607 32-bit Systems 10.0.14393.0 < 10.0.14393.8783

Windows 10 Version 1809 32-bit Systems 10.0.17763.0 < 10.0.17763.8276

Windows 10 Version 21H2 32-bit Systems 10.0.19044.0 < 10.0.19044.6809

References

https://msrc.microsoft.com/update-guide/vulnerability/CVE...
vendor-advisorypatch

CVSS V3.1

Score:
8.1
Severity:
HIGH
Confidentiality:
High
Integrity:
High
Availability:
High
Attack Vector:
Network
Attack Complexity:
High
Privileges Required:
None
User Interaction:
None
Scope:
Unchanged

Timeline

  • Vulnerability published

  • Vulnerability Reserved

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