CVE-2026-78509 json
Microsoft Office Outlook Remote Code Execution Vulnerability
published 2026-09-08 2 mo ago modified 2026-10-31 8 d ago also EUVD-2026-73313
- cvss
- 9.8
- version 3.1, CNA
- cisa kev
- Not listed
- not in CISA's catalog
- epss
- 1.0%
- EPSS 1.0% chance of exploitation in 30 days, percentile 62%
- public exploits
- 0
- none known
Summary
Heap-based buffer overflow in Microsoft Office Outlook allows an unauthorized attacker to execute code over a network.
Patch / fix
- Microsoft Microsoft 365 Apps for Enterprise 16.0.20326.20138
- Microsoft Microsoft Office 2019 16.0.10417.20207
- Microsoft Microsoft Office 365 for Mac 16.113.26091433
- Microsoft Microsoft Office LTSC 2021 16.0.14334.20906
- Microsoft Microsoft Office LTSC 2024 16.0.17932.20976
- Microsoft Microsoft Office LTSC for Mac 2021 16.113.26091433
- Microsoft Microsoft Office LTSC for Mac 2024 16.113.26091433
- Microsoft Microsoft Word 2016 16.0.5569.1000
CISA SSVC
- Exploitation
- none
- Automatable
- yes
- Technical impact
- total
- Assessed
- 2 mo ago
Exploit prediction
0.97% chance of exploitation in the next 30 days, higher than 62% of all scored CVEs (FIRST EPSS, 2026-11-08).
CVSS scores
| assigned by | version | score | vector |
|---|---|---|---|
| CNA | 3.1 | 9.8 | 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 |
| CNA | 3.1 | 9.8 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H |
Affected products
- Microsoft Microsoft 365 Apps for Enterprise
- Microsoft Microsoft Office 2019
- Microsoft Microsoft Office 365 for Mac
- Microsoft Microsoft Office LTSC 2021
- Microsoft Microsoft Office LTSC 2024
- Microsoft Microsoft Office LTSC for Mac 2021
- Microsoft Microsoft Office LTSC for Mac 2024
- Microsoft Microsoft Word 2016
Classification
- Weakness
-
- CWE-122 Heap-based Buffer Overflow
References
-
msrc.microsoft.com
/update-guide/vulnerability/CVE-2026-78509
vendor-advisory, patch
Sources
- CVE List CVE-2026-78509
- NVD CVE-2026-78509
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