Stack-based buffer overflow in Microsoft products - CVE-2026-55134
Published: July 17, 2026
Vulnerability identifier: #VU138234
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-2026-55134
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 stack-based buffer overflow in Microsoft Office Word when parsing a crafted Office file. A remote attacker can send a specially crafted file and trick the victim into opening it to execute arbitrary code.
The Preview Pane is not an attack vector.
Affected software
Microsoft Office for macOS
Microsoft Word
Microsoft SharePoint Server
Microsoft Word
Microsoft SharePoint Server
How to mitigate CVE-2026-55134
Install security update from vendor's website.
Microsoft Office for macOS - update to 16.111.26071215
Microsoft Word - update to 16.0.5561.1000
Microsoft SharePoint Server - addressed in versions 16.0.5561.1001, 16.0.10417.20175, 16.0.19725.20434
Microsoft Word - update to 16.0.5561.1000
Microsoft SharePoint Server - addressed in versions 16.0.5561.1001, 16.0.10417.20175, 16.0.19725.20434