Summary
Impact: Spoofing. Microsoft rating: Important. Not known to be exploited — Exploitation Less Likely. Customer action: Required.
Details
According to the CVSS metrics, successful exploitation of this vulnerability could lead to major loss of confidentiality (C:H). What does that mean for this vulnerability?
This vulnerability discloses a user's NTLMv2 hash to the attacker who could use this to authenticate as the user.
How could an attacker exploit this vulnerability?
External attackers could send specially crafted emails that will cause a connection from the victim to an untrusted location of attackers' control. This will leak the Net-NTLMv2 hash of the victim to the untrusted network which an attacker can then relay to another service and authenticate as the victim.
Security updates
16.0.20625.20014 — https://support.microsoft.com/en-us/microsoft-365
10.0.14393.9688 — https://support.microsoft.com/help/5131291
10.0.17763.9487 — https://support.microsoft.com/help/5131085
10.0.19044.7846 — https://support.microsoft.com/help/5131096
10.0.20348.5870 — https://support.microsoft.com/help/5131090
10.0.22631.7711 — https://support.microsoft.com/help/5131087
10.0.26100.9974 — https://support.microsoft.com/help/5132061
10.0.26100.9911 — https://support.microsoft.com/help/5132043
10.0.26100.33822 — https://support.microsoft.com/help/5131080
10.0.26100.33730 — https://support.microsoft.com/help/5131077
10.0.28000.3501 — https://support.microsoft.com/help/5132059
Vulnerabilities 1
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High 7.5
Windows NTLM Spoofing Vulnerability
Exposure of sensitive information to an unauthorized actor in Windows NTLM allows an unauthorized attacker to perform spoofing over a network.
Revision history
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#2
Added Microsoft Office software to the Security Updates table. Customers that are running supported version of Microsoft Office are encouraged to update to the indicated version to be protected from this vulnerability.
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#1
Information published.
References
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CVE-2026-121680 Windows NTLM Spoofing Vulnerability - HTML
https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-121680
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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