Heap-based buffer overflow in Microsoft Office for macOS and Microsoft Office - CVE-2026-55140

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 when parsing a crafted Office file. A remote attacker can send a specially crafted Office file to a user and convince them to open it to execute arbitrary code.

The Preview Pane is also an attack vector, and user interaction is required.

How to mitigate CVE-2026-55140

Sources

• https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2026-55140
• https://www.microsoft.com/en-us/microsoft-365/mac/microsoft-365-for-mac?msockid=35f9adb0e74b61392038b90de6fe608c