Is CVE-2026-21249 in the CISA KEV catalog?

No. CVE-2026-21249 is not currently on the CISA Known Exploited Vulnerabilities list.

What is the CVSS severity of CVE-2026-21249?

CVE-2026-21249 has a CVSS v3 base score of 3.3 (Important).

What is the EPSS score for CVE-2026-21249?

CVE-2026-21249 has an EPSS score of 10.74% (95th percentile), estimating the probability of exploitation in the next 30 days.

How do I fix CVE-2026-21249?

Install KB5075999 for Windows 10 Version 1607. Fixes are available for 20 affected products.

CVE & CISA-KEV Catalog

CVE-2026-21249

HIGHEPSS 95th pctl

3.3

CVSS v3

NVD

Description

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

CWE-73External Control of File Name or Path

How to fix

Remediation Available

Windows 10 Version 1607Windows

Install:KB5075999Microsoft

Windows 10 Version 1809Windows

Install:KB5075904Microsoft

Windows 10 Version 21H2Windows

Install:KB5075912Microsoft

Windows 10 Version 22H2Windows

Install:KB5075912Microsoft

Windows 11 Version 23H2Windows

Install:KB5075941Microsoft

Windows 11 Version 24H2Windows

Install:KB5077212Microsoft

Install:KB5077181Microsoft

Windows 11 Version 25H2Windows

Install:KB5077181Microsoft

Install:KB5077212Microsoft

Windows 11 Version 26H1Windows

Install:KB5077179Microsoft

Windows 11 version 26H1Windows

Install:KB5077179Microsoft

Windows Server 2012 R2Windows

Install:KB5075970Microsoft

Windows Server 2012 R2 (Server Core installation)Windows

Install:KB5075970Microsoft

Windows Server 2016Windows

Install:KB5075999Microsoft

Windows Server 2016 (Server Core installation)Windows

Install:KB5075999Microsoft

Windows Server 2019Windows

Install:KB5075904Microsoft

Windows Server 2019 (Server Core installation)Windows

Install:KB5075904Microsoft

Windows Server 2022Windows

Install:KB5075943Microsoft

Install:KB5075906Microsoft

Windows Server 2022 (Server Core installation)Windows

Install:KB5075906Microsoft

Install:KB5075943Microsoft

Windows Server 2022, 23H2 Edition (Server Core installation)Windows

Install:KB5075897Microsoft

Windows Server 2025Windows

Install:KB5075942Microsoft

Install:KB5075899Microsoft

Windows Server 2025 (Server Core installation)Windows

Install:KB5075942Microsoft

Install:KB5075899Microsoft

TridentStack Control can deploy fixes like this automatically across your Windows, macOS, and Linux fleet. See how it works

Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.

CVSS v3 Vector

Exploitability

Attack VectorLocal

Attack ComplexityLow

Privileges RequiredNone

User InteractionRequired

ScopeUnchanged

Impact

ConfidentialityLow

IntegrityNone

AvailabilityNone

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

Exploit Intelligence

10.74%probability of exploitation in 30 days

95thpercentile

Very high risk: more likely to be exploited than 95% of all known CVEs.

References

Vendor Advisory1

msrc.microsoft.com

Related Vulnerabilities

Other CWE-73 (External Control of File Name or Path) vulnerabilities, ordered by exploit likelihood. View all

CVE	Severity	CVSS	EPSS	Exploited	Fix
CVE-2022-39952	Critical	9.8	100%	-	Fix
CVE-2024-8517	Critical	9.8	95%	-	Fix
CVE-2023-4634	Critical	9.8	83%	-	Fix
CVE-2018-17246	Critical	9.8	82%	-	Fix
CVE-2025-33053	High	8.8	82%	KEV	Fix
CVE-2024-43451	Medium	6.5	82%	KEV	Fix

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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-02-11.