CVE-2026-78509

CRITICAL

INFO Priority: 0.10 BB Relevance: 80/100

Published: 2026-09-08 Modified: 2026-10-30 First seen: 2026-10-30 Status: active

Network Low Complexity No Auth No Interaction Conf. Impact Integ. Impact

AV: Network

AC: Low

PR: None

UI: None

S: Unchanged

C: High

I: High

A: High

Heap-based buffer overflow in Microsoft Office Outlook allows an unauthorized attacker to execute code over a network.

Vendor	Product	Version
Microsoft	Microsoft 365 Apps for Enterprise	16.0.1 < 16.0.20326.20138
Microsoft	Microsoft Office 2019	19.0.0 < 16.0.10417.20207
Microsoft	Microsoft Office 365 for Mac	1.0.0 < 16.113.26091433
Microsoft	Microsoft Office LTSC 2021	16.0.1 < 16.0.14334.20906
Microsoft	Microsoft Office LTSC 2024	16.0.0 < 16.0.17932.20976
Microsoft	Microsoft Office LTSC for Mac 2021	16.0.1 < 16.113.26091433
Microsoft	Microsoft Office LTSC for Mac 2024	16.0.0 < 16.113.26091433
Microsoft	Microsoft Word 2016	16.0.1 < 16.0.5569.1000

vendor-advisory patch

80 / 100

✓ Network accessible
✓ No authentication
✓ Low complexity
✓ No user interaction

9.8 / 10.0 v3.1

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

0.97%

Raw Score 0.009740

Percentile 62.0%

Date 2026-10-30

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