CRITICAL 9.8 Microsoft
CVE-2026-78509
Microsoft Office Outlook Remote Code Execution Vulnerability
Microsoft Security Update 2026-Sep: Microsoft Office Outlook Remote Code Execution Vulnerability
Affected Products
- Microsoft Office 365 for Mac
- Microsoft Office 2019 for 32-bit editions
- Microsoft Office 2019 for 64-bit editions
- Microsoft 365 Apps for Enterprise for 32-bit Systems
- Microsoft 365 Apps for Enterprise for 64-bit Systems
- Microsoft Office LTSC for Mac 2021
- Microsoft Office LTSC 2021 for 64-bit editions
- Microsoft Office LTSC 2021 for 32-bit editions
References
- https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-78509
- https://nvd.nist.gov/vuln/detail/CVE-2026-78509
This critical severity vulnerability with a CVSS score of 9.8 was published on 2026-09-08 via Microsoft. Affected: Microsoft Office 365 for Mac, Microsoft Office 2019 for 32-bit editions, Microsoft Office 2019 for 64-bit editions and 5 more.
Risk Timeline
CVE Disclosed2026-09-08 · 48 days ago
Remediation Resources
Official Advisory
msrc.microsoft.com/update-guide/vulnerability/CVE-2026-78509NVD / MITRE
nvd.nist.gov/vuln/detail/CVE-2026-78509Related Vulnerabilities
| CVE | Title | Severity | CVSS |
|---|---|---|---|
| CVE-2026-96207 | Microsoft Partner Center Elevation of Privilege Vulnerability | CRITICAL | 10.0 |
| CVE-2026-63508 | Microsoft Planetary Computer Pro Elevation of Privilege Vulnerability | CRITICAL | 10.0 |
| 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 |
| CVE-2026-69836 | Microsoft Entra ID Remote Code Execution Vulnerability | CRITICAL | 10.0 |
| CVE-2026-56191 | Microsoft Exchange Online Tampering Vulnerability | CRITICAL | 10.0 |
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