Summary
Impact: Spoofing. Microsoft rating: Important. Not known to be exploited — Exploitation Less Likely. Customer action: Required.
Details
According to the CVSS metric, user interaction is required (UI:R). What interaction would the user have to do?
An attacker must send a user a malicious Office file and convince them to open it.
According to the CVSS metrics, successful exploitation of this vulnerability could lead to some loss of confidentiality (C:L),but lead to no loss of availability (A:N) and integrity (I:N)? What does that mean for this vulnerability?
An attacker who successfully exploited the vulnerability could view some sensitive information (Confidentiality) but not all resources within the impacted component may be divulged to the attacker. The attacker cannot make changes to disclosed information (Integrity) or limit access to the resource (Availability).
Security updates
10.0.28000.1575 — https://support.microsoft.com/help/5077179
10.0.17763.8389 — https://support.microsoft.com/help/5075904
10.0.20348.4773 — https://support.microsoft.com/help/5075906
10.0.20348.4711 — https://support.microsoft.com/help/5075943
10.0.19044.6937 — https://support.microsoft.com/help/5075912
10.0.26100.32370 — https://support.microsoft.com/help/5075899
10.0.26100.32313 — https://support.microsoft.com/help/5075942
10.0.26200.7840 — https://support.microsoft.com/help/5077181
10.0.26200.7781 — https://support.microsoft.com/help/5077212
10.0.22631.6649 — https://support.microsoft.com/help/5075941
10.0.25398.2149 — https://support.microsoft.com/help/5075897
10.0.14393.8868 — https://support.microsoft.com/help/5075999
6.3.9600.23022 — https://support.microsoft.com/help/5075970
Vulnerabilities 1
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Low 3.3CVE-2026-21249 EPSS 11%
Windows NTLM Spoofing Vulnerability
External control of file name or path in Windows NTLM allows an unauthorized attacker to perform spoofing locally.
Revision history
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#1
Information published.
References
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CVE-2026-21249 Windows NTLM Spoofing Vulnerability - HTML
https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-21249
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Microsoft Exploitability Index
https://www.microsoft.com/en-us/msrc/exploitability-index?rtc=1
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Microsoft Support Lifecycle
https://support.microsoft.com/lifecycle
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Common Vulnerability Scoring System
https://www.first.org/cvss