CVE-2026-21249: Windows NTLM Spoofing Vulnerability

Published Feb 10, 2026
·
Updated

External control of file name or path in Windows NTLM allows an unauthorized attacker to perform spoofing locally.

Affected Software

51 affected componentsFixes available
Microsoft Windows Server 2012 R2
Microsoft Windows Server 2025
Microsoft Windows 11=24H2
Microsoft Windows Server 2022, 23H2 Edition
Microsoft Windows Server 2012 R2
Microsoft Windows 11=23H2
Microsoft Windows 10=1607
Microsoft Windows Server 2016
Microsoft Windows 11=24H2
Microsoft Windows 10=1607
Microsoft Windows 11=23H2
Microsoft Windows 11=25H2
Microsoft Windows Server 2025
Microsoft Windows 10=22H2
Microsoft Windows 11=25H2
Microsoft Windows 10=22H2
Microsoft Windows 10=21H2
Microsoft Windows 10=22H2
Microsoft Windows 10=21H2
Microsoft Windows Server 2019
Microsoft Windows Server 2016
Microsoft Windows 10=21H2
Microsoft Windows Server 2022
Microsoft Windows 10=1809
Microsoft Windows Server 2022
Microsoft Windows Server 2019
Microsoft Windows 11=26H1
Microsoft Windows 11=26H1
Microsoft Windows 10=1809
Microsoft Windows 10 1607<10.0.14393.8868
Microsoft Windows 10 1607<10.0.14393.8868
Microsoft Windows 10 1809<10.0.17763.8389
Microsoft Windows 10 1809<10.0.17763.8389
Microsoft Windows 10 21h2<10.0.19044.6937
Microsoft Windows 10 21h2<10.0.19044.6937
Microsoft Windows 10 21h2<10.0.19044.6937
Microsoft Windows 10 22h2<10.0.19045.6937
Microsoft Windows 10 22h2<10.0.19045.6937
Microsoft Windows 10 22h2<10.0.19045.6937
Microsoft Windows 11 23h2<10.0.22631.6649
Microsoft Windows 11 23h2<10.0.22631.6649
Microsoft Windows 11 24h2<10.0.26100.7781
Microsoft Windows 11 24h2<10.0.26100.7781
Microsoft Windows 11 25h2<10.0.26200.7781
Microsoft Windows 11 25h2<10.0.26200.7781
Microsoft Windows Server 2012=r2
Microsoft Windows Server 2016<10.0.14393.8868
Microsoft Windows Server 2019<10.0.17763.8389
Microsoft Windows Server 2022<10.0.20348.4711
Microsoft Windows Server 2022 23h2<10.0.25398.2149
Microsoft Windows Server 2025<10.0.26100.32313

Event History

Feb 10, 2026
CVE Published
via Microsoft·04:00 PM
Data Sourced
via Microsoft·04:00 PM
DescriptionSeverityWeaknessAffected Software
Updated
via Microsoft·04:00 PM
Affected Software
Updated
via Microsoft·04:00 PM
Description
CVE Published
via MITRE·05:51 PM
Data Sourced
via MITRE·05:51 PM
DescriptionSeverity
Data Sourced
via NVD·06:16 PM
DescriptionSeverityWeaknessAffected Software
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Frequently Asked Questions

1

What is the severity of CVE-2026-21249?

CVE-2026-21249 is considered a critical vulnerability due to its potential for unauthorized access and local spoofing attacks.

2

How do I fix CVE-2026-21249?

To fix CVE-2026-21249, apply the relevant security updates provided by Microsoft for your specific Windows version or edition.

3

Which versions of Windows are affected by CVE-2026-21249?

CVE-2026-21249 affects multiple Windows versions including Windows Server 2012 R2, Windows Server 2025, Windows 10, and Windows 11 among others.

4

How can I determine if my system is vulnerable to CVE-2026-21249?

You can determine vulnerability by checking if your Windows system is running an affected version and if it has the required updates installed.

5

What impact does CVE-2026-21249 have on Windows systems?

CVE-2026-21249 allows an unauthorized attacker to locally spoof accounts, potentially compromising the integrity of the system.

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