Windows NTLM
CVE-2026-21249 — Windows NTLM Spoofing Vulnerability
Executive Summary
External control of file name or path in Windows NTLM allows an unauthorized attacker to perform spoofing locally.
Overview
3.3
CVSS LOW
Important
MS Severity
Not Exploited
MS Exploit Status
Less Likely
MS Exploit Likelihood
CVSS Vector
ATTACK VECTOR
Local
ATTACK COMPLEXITY
Low
PRIVILEGES REQUIRED
None
USER INTERACTION
Required
SCOPE
Unchanged
Temporal Score: 2.9
EPSS Score
0.11356
probability of exploitation in the next 30 days
0.95432 percentile - updated 2026-06-20
View on FIRST.org
Affected Products
29 affected products
| Product | KB Article | Severity | Impact | Restart Required |
|---|---|---|---|---|
| Windows 10 Version 1607 for 32-bit Systems | 5075999 (Security Update) |
Important | Spoofing | Yes |
| Windows 10 Version 1607 for x64-based Systems | 5075999 (Security Update) |
Important | Spoofing | Yes |
| Windows 10 Version 1809 for 32-bit Systems | 5075904 (Security Update) |
Important | Spoofing | Yes |
| Windows 10 Version 1809 for x64-based Systems | 5075904 (Security Update) |
Important | Spoofing | Yes |
| Windows 10 Version 21H2 for 32-bit Systems | 5075912 (Security Update) |
Important | Spoofing | Yes |
| Windows 10 Version 21H2 for ARM64-based Systems | 5075912 (Security Update) |
Important | Spoofing | Yes |
| Windows 10 Version 21H2 for x64-based Systems | 5075912 (Security Update) |
Important | Spoofing | Yes |
| Windows 10 Version 22H2 for 32-bit Systems | 5075912 (Security Update) |
Important | Spoofing | Yes |
| Windows 10 Version 22H2 for ARM64-based Systems | 5075912 (Security Update) |
Important | Spoofing | Yes |
| Windows 10 Version 22H2 for x64-based Systems | 5075912 (Security Update) |
Important | Spoofing | Yes |
| Windows 11 Version 23H2 for ARM64-based Systems | 5075941 (Security Update) |
Important | Spoofing | Yes |
| Windows 11 Version 23H2 for x64-based Systems | 5075941 (Security Update) |
Important | Spoofing | Yes |
| Windows 11 Version 24H2 for ARM64-based Systems | 5077181 (Security Update) 5077212 (Security Hotpatch Update) |
Important | Spoofing | Yes |
| Windows 11 Version 24H2 for x64-based Systems | 5077212 (Security Hotpatch Update) 5077181 (Security Update) |
Important | Spoofing | Yes |
| Windows 11 Version 25H2 for ARM64-based Systems | 5077181 (Security Update) 5077212 (Security Hotpatch Update) |
Important | Spoofing | Yes |
| Windows 11 Version 25H2 for x64-based Systems | 5077181 (Security Update) 5077212 (Security Hotpatch Update) |
Important | Spoofing | Yes |
| Windows 11 Version 26H1 for ARM64-based Systems | 5077179 (Security Update) |
Important | Spoofing | Yes |
| Windows 11 version 26H1 for x64-based Systems | 5077179 (Security Update) |
Important | Spoofing | Yes |
| Windows Server 2012 R2 | 5075970 (Monthly Rollup) |
Important | Spoofing | Yes |
| Windows Server 2012 R2 (Server Core installation) | 5075970 (Monthly Rollup) |
Important | Spoofing | Yes |
| Windows Server 2016 | 5075999 (Security Update) |
Important | Spoofing | Yes |
| Windows Server 2016 (Server Core installation) | 5075999 (Security Update) |
Important | Spoofing | Yes |
| Windows Server 2019 | 5075904 (Security Update) |
Important | Spoofing | Yes |
| Windows Server 2019 (Server Core installation) | 5075904 (Security Update) |
Important | Spoofing | Yes |
| Windows Server 2022 | 5075906 (Security Update) 5075943 (Security Hotpatch Update) |
Important | Spoofing | Yes |
| Windows Server 2022 (Server Core installation) | 5075906 (Security Update) 5075943 (Security Hotpatch Update) |
Important | Spoofing | Yes |
| Windows Server 2022, 23H2 Edition (Server Core installation) | 5075897 (Security Update) |
Important | Spoofing | Yes |
| Windows Server 2025 | 5075899 (Security Update) 5075942 (Security Hotpatch Update) |
Important | Spoofing | Yes |
| Windows Server 2025 (Server Core installation) | 5075899 (Security Update) 5075942 (Security Hotpatch Update) |
Important | Spoofing | Yes |
Patches
11 patches
| Article | Type | Restart |
|---|---|---|
5075999 |
Security Update | Yes |
5075904 |
Security Update | Yes |
5075912 |
Security Update | Yes |
5075941 |
Security Update | Yes |
5077181 (Security Update) 5077212 |
Security Update | Yes |
5077212 (Security Hotpatch Update) 5077181 |
Security Hotpatch Update | Yes |
5077179 |
Security Update | Yes |
5075970 |
Monthly Rollup | Yes |
5075906 (Security Update) 5075943 |
Security Update | Yes |
5075897 |
Security Update | Yes |
5075899 (Security Update) 5075942 |
Security Update | Yes |
Known Exploits
No known exploits have been linked for this CVE yet. When available, exploit references will be sourced from public repositories and may be unverified, incomplete, or non-functional. Always review code carefully before use in any environment.
Acknowledgments
Joe Desimone with Elastic Security, Jonathan Lein of TrendAI Research, Jonathan Lein of TrendAI Research
References
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