CVE-2026-21249 Details
Description
External control of file name or path in Windows NTLM allows an unauthorized attacker to perform spoofing locally.
A spoofing vulnerability has been identified in Windows NTLM, allowing an unauthorized attacker to manipulate file names or paths and perform spoofing locally. This issue affects multiple Windows products and versions, including various editions of Windows Server, Windows 10, and Windows 11. The vulnerability arises from external control of file names or paths, which can be exploited by sending a malicious Office file to a user and convincing them to open it.
Users can apply the security update for this vulnerability, which is available through the Microsoft Update Catalog. Specific update details can be found in the Microsoft Knowledge Base articles linked in the product-specific update guidance.
Metrics
CVSS 4.0 Severity and Vector Strings:
No CVSS 4.0 data is available for this CVE.
CVSS 3.x Severity and Vector Strings:
No data available for CVSS Version 2.0 on this CVE.
CISA-ADP
Assessed Feb 11, 2026References to Advisories, Solutions, and Tools
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| URL | Source(s) | Tag(s) |
|---|---|---|
| https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-21249 | [email protected] | Vendor Advisory |
Weakness Enumeration
| CWE-ID | CWE Name | Source |
|---|---|---|
| CWE-73 | External Control of File Name or Path | [email protected] |
Affected Products
| Product | Versions |
|---|---|
| microsoft windows 10 1607 | < 10.0.14393.8868 |
CPE
Remediation
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| microsoft windows 10 1809 | < 10.0.17763.8389 |
CPE
Remediation
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| microsoft windows 10 21h2 | < 10.0.19044.6937 |
CPE
Remediation
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| microsoft windows 10 22h2 | < 10.0.19045.6937 |
CPE
Remediation
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| microsoft windows 11 23h2 | < 10.0.22631.6649 |
CPE
Remediation
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| microsoft windows 11 24h2 | < 10.0.26100.7781 |
CPE
Remediation
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| microsoft windows 11 25h2 | < 10.0.26200.7781 |
CPE
Remediation
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| microsoft windows server 2012 | r2 |
CPE
Remediation
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| microsoft windows server 2016 | < 10.0.14393.8868 |
CPE
Remediation
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| microsoft windows server 2019 | < 10.0.17763.8389 |
CPE
Remediation
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| microsoft windows server 2022 | < 10.0.20348.4711 |
CPE
Remediation
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| microsoft windows server 2022 23h2 | < 10.0.25398.2149 |
CPE
Remediation
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| microsoft windows server 2025 | < 10.0.26100.32313 |
CPE
Remediation
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Change History
4 change records found show changes
| Date | Action | Recorded By |
|---|---|---|
| Jun 17, 2026 | CVE Modified | [email protected] |
| Jun 17, 2026 | CVE Modified | CISA-ADP |
| Feb 11, 2026 | Initial Analysis | [email protected] |
| Feb 10, 2026 | New CVE Received | [email protected] |