CRITICAL 9.8 NVD

CVE-2026-78509

Heap-based buffer overflow in Microsoft Office Outlook allows an unauthorized attacker to execute code over a network.

Affected Products

microsoft/365_apps
microsoft/microsoft_365
microsoft/office_2019
microsoft/office_2021
microsoft/office_2024
microsoft/word

References

https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-78509

Published: 2026-09-08 · Source: NVD · Feed updated: 2026-09-11

This critical severity vulnerability with a CVSS score of 9.8 was published on 2026-09-08 via NVD. Affected: microsoft/365_apps, microsoft/microsoft_365, microsoft/office_2019 and 3 more.

Risk Timeline

CVE Disclosed2026-09-08 · 2 days ago

Remediation Resources

Official Advisory

msrc.microsoft.com/update-guide/vulnerability/CVE-2026-78509

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CVE-2026-65667	Microsoft Teams Elevation of Privilege Vulnerability	CRITICAL	10.0
CVE-2026-65801	Microsoft Exchange Online Elevation of Privilege Vulnerability	CRITICAL	10.0
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