Race Condition Vulnerability in Windows SMB Server by Microsoft
CVE-2026-20921

7.5HIGH

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-2026-20921?

A race condition vulnerability exists in the Windows SMB Server, where improper synchronization of shared resources can be exploited by an authorized attacker to elevate privileges over a network. This flaw allows attackers to manipulate the server’s execution flow, potentially gaining access to sensitive data and resources not normally accessible under their current privileges. It is crucial to apply the recommended patches to mitigate this risk.

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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:
7.5
Severity:
HIGH
Confidentiality:
High
Integrity:
High
Availability:
High
Attack Vector:
Network
Attack Complexity:
High
Privileges Required:
Low
User Interaction:
None
Scope:
Unchanged

Timeline

  • Vulnerability published

  • Vulnerability Reserved

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