Summary
Impact: Remote Code Execution. 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, the attack complexity is high (AC:H). What does that mean for this vulnerability?
Successful exploitation requires the targeted system to have sufficient available memory to process a large, specially crafted message.
Security updates
16.0.14334.21048 — https://docs.microsoft.com/en-us/officeupdates/microsoft365-apps-security-updates
https — https://learn.microsoft.com/en-us/officeupdates/microsoft365-apps-security-updates
Vulnerabilities 1
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High 7.5
Microsoft Office Outlook Remote Code Execution Vulnerability
Heap-based buffer overflow 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-2026-123379 Microsoft Office Outlook Remote Code Execution Vulnerability - HTML
https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-123379
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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