CVE-2026-78509
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.
Attack profile
How easy it is to exploit
- Attack vector
- Network
- Complexity
- Low
- Privileges needed
- None
- User interaction
- None
What an attacker can affect
- Confidentiality
- High
- Integrity
- High
- Availability
- High
Exploit likelihood
What each source reports
CVE List Score used
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.
- Record
CVE-2026-78509- CVSS 3.1
- 9.8 Critical
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C - Weakness
- CWE-122
- Updated
- 2026-11-02
EUVDEUVD-2026-73313
Heap-based buffer overflow in Microsoft Office Outlook allows an unauthorized attacker to execute code over a network.
- Record
EUVD-2026-73313- CVSS 3.1
- 9.8 Critical
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C - Updated
- 2026-11-02
GitHub AdvisoriesGHSA-8rh6-mjg6-wf8q
Heap-based buffer overflow in Microsoft Office Outlook allows an unauthorized attacker to execute...
Heap-based buffer overflow in Microsoft Office Outlook allows an unauthorized attacker to execute code over a network.
- Record
GHSA-8rh6-mjg6-wf8q- CVSS 3.1
- 9.8 Critical
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H - Weakness
- CWE-122
- Updated
- 2026-11-02
NVD
Heap-based buffer overflow in Microsoft Office Outlook allows an unauthorized attacker to execute code over a network.
- Record
CVE-2026-78509- CVSS 3.1
- 9.8 Critical
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H - Weakness
- CWE-122
- Updated
- 2026-11-02
Affected products
- microsoft 365 apps
- microsoft 365 apps for enterprise
- microsoft office 2019
- microsoft office 365 for mac
- microsoft office ltsc 2021
- microsoft office ltsc 2024
- microsoft office ltsc for mac 2021
- microsoft office ltsc for mac 2024
- microsoft word 2016
- microsoft 365
- microsoft office 2021
- microsoft office 2024
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History
| Recorded | Changed | Sources |
|---|---|---|
| first indexed | CVE List, EUVD, GitHub Advisories, NVD |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2026-78509 is a critical vulnerability (CVSS 9.8) in Microsoft 365 Apps, published September 8, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.97%, the 62nd percentile. No source names a fixed version.