MicrosoftCVE-2026-78509
Microsoft Office Outlook: heap buffer overflow
Critical9.8CVE-2026-78509 · Published Sep 8, 2026 · updated Sep 17, 2026
Heap-based buffer overflow in Microsoft Office Outlook allows an unauthorized attacker to execute code over a network.
Affected versions
| Package | Affected | Fixed in |
|---|---|---|
| Microsoft 365 Apps for Enterprise Product | >= 16.0.1, < 16.0.20326.20138 | 16.0.20326.20138 |
| Microsoft Office 2019 Product | >= 19.0.0, < 16.0.10417.20207 | 16.0.10417.20207 |
| Microsoft Office 365 for Mac Product | >= 1.0.0, < 16.113.26091433 | 16.113.26091433 |
| Microsoft Office LTSC 2021 Product | >= 16.0.1, < 16.0.14334.20906 | 16.0.14334.20906 |
| Microsoft Office LTSC 2024 Product | >= 16.0.0, < 16.0.17932.20976 | 16.0.17932.20976 |
| Microsoft Office LTSC for Mac 2021 Product | >= 16.0.1, < 16.113.26091433 | 16.113.26091433 |
| Microsoft Office LTSC for Mac 2024 Product | >= 16.0.0, < 16.113.26091433 | 16.113.26091433 |
| Microsoft Word 2016 Product | >= 16.0.1, < 16.0.5569.1000 | 16.0.5569.1000 |
Details and references
- CVSS 3.1
- CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- Severity from
- the vendor (its own CVE record or advisory)
- Weakness
- CWE-122
More Microsoft advisories
All Microsoft| Date | Advisory | Severity | Fixed in |
|---|---|---|---|
| Sep 8 | Microsoft Skype for Business: spoofing | High8.3 | 6.0.9319.885+2 more |
| Sep 8 | Microsoft Skype for Business: cross-site scripting | Medium6.5 | 6.0.9319.885+2 more |
| Sep 8 | Microsoft Skype for Business: spoofing | High7.1 | 6.0.9319.885+2 more |
| Sep 8 | Microsoft Skype for Business: information disclosure | Medium6.5 | 6.0.9319.885+2 more |
| Sep 8 | Microsoft Skype for Business: integer overflow | High7.5 | 6.0.9319.885+2 more |
| Sep 8 | Microsoft Skype for Business: out-of-bounds read | Medium6.5 | 6.0.9319.885+2 more |