Stack-based buffer overflow in Microsoft products - CVE-2026-78504
Published: September 9, 2026
Vulnerability identifier: #VU148222
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-2026-78504
CWE-ID: CWE-121
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 stack-based buffer overflow in Microsoft Office Word when opening a malicious Office file. A remote attacker can send a malicious Office file and convince a user to open it to execute arbitrary code.
The Preview Pane is not an attack vector.
Affected software
Microsoft Word
Microsoft 365 Apps for Enterprise
Microsoft Office
Microsoft 365 Apps for Enterprise
Microsoft Office
How to mitigate CVE-2026-78504
Install security update from vendor's website.
Microsoft Word - update to 16.0.5569.1000
Microsoft 365 Apps for Enterprise - update to 16.0.20326.20138
Microsoft Office - addressed in versions 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 16.0.10417.20207, 16.0.14334.20906, 16.0.17932.20976