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?
A user interacting with the file in multiple ways will cause the NTLM hash to be leaked. A few interactions which trigger this leak include:
Opening the parent folder in Explorer, Clicking the file (any mouse button), Dragging the file, Deleting the file
Security updates
https — https://docs.microsoft.com/en-us/officeupdates/microsoft365-apps-security-updates
https — https://learn.microsoft.com/en-us/officeupdates/microsoft365-apps-security-updates
16.0.5569.1003 — https://support.microsoft.com/help/5002916
Vulnerabilities 1
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Medium 6.5
Microsoft Office Spoofing Vulnerability
Insufficiently protected credentials in Microsoft Office allows an unauthorized attacker to perform spoofing over a network.
Revision history
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#1
Information published.
References
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CVE-2026-64918 Microsoft Office Spoofing Vulnerability - HTML
https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-64918
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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