Heap-based buffer overflow in Microsoft Office for macOS - CVE-2026-55133
Published: July 17, 2026
Vulnerability identifier: #VU138243
CSH Severity: High
CVSS v4.0: 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/E:U/U:Amber
CVE-ID: CVE-2026-55133
CWE-ID: CWE-122
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vendor: Microsoft
Affected software:
Microsoft Office for macOS
Microsoft Office for macOS
Detailed vulnerability description
The vulnerability allows a remote attacker to execute arbitrary code.
The vulnerability exists due to heap-based buffer overflow in Microsoft Office OneNote when parsing a crafted Office file. A remote attacker can send a specially crafted file to a user and convince them to open it to execute arbitrary code.
User interaction is required to open a crafted file, and the Preview Pane is not an attack vector.
How to mitigate CVE-2026-55133
Install security update from vendor's website.