Summary
Impact: Remote Code Execution. Microsoft rating: Critical. Not known to be exploited — Exploitation Less Likely. Customer action: Required.
Details
How could an attacker exploit the vulnerability?
In an email attack scenario, an attacker could exploit the vulnerability by sending the specially crafted email to the victim. Exploitation of the vulnerability might involve either a victim opening a specially crafted email with an affected version of Microsoft Outlook software, or a victim's Outlook application displaying a preview of a specially crafted email . This could result in the attacker executing remote code on the victim's machine.
Is the Preview Pane an attack vector for this vulnerability?
Yes, the Preview Pane is an attack vector.
Security updates
16.0.10417.20207 — https://docs.microsoft.com/en-us/officeupdates/microsoft365-apps-security-updates
16.0.20326.20138 — https://docs.microsoft.com/en-us/officeupdates/office365-proplus-security-updates
16.0.5569.1000 — https://support.microsoft.com/help/5002919
Vulnerabilities 1
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High 8.8
Microsoft Office Outlook Remote Code Execution Vulnerability
Use of uninitialized resource in Microsoft Office Outlook allows an unauthorized attacker to execute code over a network.
Revision history
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#1
Information published.
References
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CVE-2026-78519 Microsoft Office Outlook Remote Code Execution Vulnerability - HTML
https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-78519
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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