Summary
Impact: Elevation of Privilege. Microsoft rating: Important. Not known to be exploited — Exploitation Less Likely. Customer action: Required.
Details
Is the Preview Pane an attack vector for this vulnerability?
No, the Preview Pane is not an attack vector.
According to the CVSS metric, a successful exploitation could lead to a scope change (S:C). What does this mean for this vulnerability?
This vulnerability could lead to a browser sandbox escape.
What privileges could be gained by an attacker who successfully exploited this vulnerability?
An attacker who successfully exploited this vulnerability could gain SYSTEM privileges.
Security updates
https — https://docs.microsoft.com/en-us/officeupdates/microsoft365-apps-security-updates
Vulnerabilities 1
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High 8.8
Microsoft Office Click-To-Run Elevation of Privilege Vulnerability
Use after free in Microsoft Office allows an authorized attacker to elevate privileges locally.
Revision history
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#1
Information published.
References
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CVE-2026-40420 Microsoft Office Click-To-Run Elevation of Privilege Vulnerability - HTML
https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-40420
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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