Summary
Impact: Elevation of Privilege. Microsoft rating: Important. Not known to be exploited — Exploitation Less Likely. Customer action: Required.
Details
What privileges could be gained by an attacker who successfully exploited the vulnerability?
An attacker who successfully exploited this vulnerability could gain administrator privileges.
Is the Preview Pane an attack vector for this vulnerability?
No, the Preview Pane is not an attack vector.
Security updates
16.0.10417.20097 — https://support.microsoft.com/help/5002835
https — https://docs.microsoft.com/en-us/officeupdates/microsoft365-apps-security-updates
16.0.5539.1002 — https://support.microsoft.com/help/5002837
Vulnerabilities 1
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High 7.8
Microsoft Excel Elevation of Privilege Vulnerability
Heap-based buffer overflow in Microsoft Office Excel allows an unauthorized attacker to elevate privileges locally.
Revision history
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#1
Information published.
References
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CVE-2026-21259 Microsoft Excel Elevation of Privilege Vulnerability - HTML
https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-21259
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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