Heap-based buffer overflow in Microsoft products - CVE-2026-78505
Published: September 9, 2026
Vulnerability identifier: #VU148223
CSH Severity: High
CVSS v4: 8.4 [CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:A/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-78505
CWE-ID: CWE-122
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote attacker to execute arbitrary code.
The vulnerability exists due to a heap-based buffer overflow in Microsoft Office for macOS when processing a specially crafted Microsoft Office document. A remote attacker can convince a user to open and save a specially crafted Microsoft Office document to execute arbitrary code.
The Preview Pane is an attack vector.
Affected software
Microsoft Office for macOS
Microsoft 365 Apps for Enterprise
Microsoft Office
Microsoft 365 Apps for Enterprise
Microsoft Office
How to mitigate CVE-2026-78505
Install security update from vendor's website.
Microsoft Office for macOS - update to 16.112.26083020
Microsoft 365 Apps for Enterprise - update to 16.0.20326.20138
Microsoft Office - addressed in versions 16.0.5569.1000, 16.0.10417.20207, 16.0.14334.20906, 16.0.17932.20976
Microsoft 365 Apps for Enterprise - update to 16.0.20326.20138
Microsoft Office - addressed in versions 16.0.5569.1000, 16.0.10417.20207, 16.0.14334.20906, 16.0.17932.20976