How severe is CVE-2026-21249?

CVE-2026-21249 has a CVSS 3.1 base score of 3.3 (LOW). EPSS estimates a 11.4% probability of exploitation in the next 30 days.

CVE-2026-21249: Windows NTLM Spoofing

Description

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

Severity

CVSS 3.1 · CNA3.3 LOW

CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:N/E:U/RL:O/RC:C

SSVC · CISA-ADP

Exploitationnone

Automatableno

Technical impactpartial

Affected Products

Vendor	Product	Affected versions
Microsoft	Windows 10 Version 1607	10.0.14393.0 to <10.0.14393.8868
Microsoft	Windows 10 Version 1809	10.0.17763.0 to <10.0.17763.8389
Microsoft	Windows 10 Version 21H2	10.0.19044.0 to <10.0.19044.6937
Microsoft	Windows 10 Version 22H2	10.0.19045.0 to <10.0.19045.6937
Microsoft	Windows 11 version 22H3	10.0.22631.0 to <10.0.22631.6649
Microsoft	Windows 11 Version 23H2	10.0.22631.0 to <10.0.22631.6649
Microsoft	Windows 11 Version 24H2	10.0.26100.0 to <10.0.26100.7840
Microsoft	Windows 11 Version 25H2	10.0.26200.0 to <10.0.26200.7840
Microsoft	Windows 11 version 26H1	10.0.28000.0 to <10.0.28000.1575
Microsoft	Windows 11 Version 26H1	10.0.28000.0 to <10.0.28000.1575
Microsoft	Windows Server 2012 R2	6.3.9600.0 to <6.3.9600.23022
Microsoft	Windows Server 2012 R2 (Server Core installation)	6.3.9600.0 to <6.3.9600.23022
Microsoft	Windows Server 2016	10.0.14393.0 to <10.0.14393.8868
Microsoft	Windows Server 2016 (Server Core installation)	10.0.14393.0 to <10.0.14393.8868
Microsoft	Windows Server 2019	10.0.17763.0 to <10.0.17763.8389
Microsoft	Windows Server 2019 (Server Core installation)	10.0.17763.0 to <10.0.17763.8389
Microsoft	Windows Server 2022	10.0.20348.0 to <10.0.20348.4773
Microsoft	Windows Server 2022, 23H2 Edition (Server Core installation)	10.0.25398.0 to <10.0.25398.2149
Microsoft	Windows Server 2025	10.0.26100.0 to <10.0.26100.32370
Microsoft	Windows Server 2025 (Server Core installation)	10.0.26100.0 to <10.0.26100.32370

References

1 Links

Vendor advisories

Windows NTLM Spoofing Vulnerability

Record Details

Published

2026-02-10

Last updated

2026-08-19

Assigner (CNA)

microsoft

Credited to

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Related Tool Categories

Tool categories that test for or protect against this vulnerability class.

CWE-73 · External Control of File Name or Path

Application Security Tools

CVE record data © The MITRE Corporation, used under the CVE Terms of Use. Exploited-in-the-wild data from the CISA Known Exploited Vulnerabilities catalog (CC0). Exploit prediction scores by FIRST EPSS (first.org/epss). This site is not endorsed or certified by MITRE, NVD, CISA, or FIRST.