Vulnerability Intelligence Report
Microsoft Office Outlook Remote Code Execution Vulnerability
CVE-2026-78509
Heap-based buffer overflow in Microsoft Office Outlook allows an unauthorized attacker to execute code over a network.
No Active Exploit Signals
CVSS Base Score
9.8
CRITICAL
Exploitability:3.9
Impact Score:5.9
EPSS Probability:0.95%
Executive Threat Verdict
Evaluating...
Evaluating Threat Landscape...
Assessing known weaponization, exploitation telemetry, and federal advisories.
Attack Surface
—
Authentication
—
Weaponization
—
SSVC Action
—
Weaknesses (CWE)
CWE-122 ↗CWE-122: Heap-based Buffer Overflow
Affected Products & Versions
| Vendor | Product | Affected Versions |
|---|---|---|
| Microsoft | Microsoft 365 Apps for Enterprise | 16.0.1 < 16.0.20326.20138 (affected) |
| Microsoft | Microsoft Office 2019 | 19.0.0 < 16.0.10417.20207 (affected) |
| Microsoft | Microsoft Office 365 for Mac | 1.0.0 < 16.113.26091433 (affected) |
| Microsoft | Microsoft Office LTSC 2021 | 16.0.1 < 16.0.14334.20906 (affected) |
| Microsoft | Microsoft Office LTSC 2024 | 16.0.0 < 16.0.17932.20976 (affected) |
| Microsoft | Microsoft Office LTSC for Mac 2021 | 16.0.1 < 16.113.26091433 (affected) |
| Microsoft | Microsoft Office LTSC for Mac 2024 | 16.0.0 < 16.113.26091433 (affected) |
| Microsoft | Microsoft Word 2016 | 16.0.1 < 16.0.5569.1000 (affected) |
References & Technical Advisories
No reference links found.
Threat Intelligence Signals
EPSS Score
0.954%
GitHub Advisory
Identity & Timeline
| Status | PUBLISHED |
| Assigning Authority | Microsoft Corporation · Vendor · USA |
| Reserved | 2026-08-24T17:28:00 |
| Published | 2026-09-08T17:13:46 |
| Patch Date | 2026-09-08 |
| Last Updated | 2026-09-18T20:41:17 |
Community Chatter & Buzz