Heap-based buffer overflow in Microsoft products - CVE-2026-118721
Published: November 11, 2026
Vulnerability identifier: #VU165126
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-2026-118721
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 with the permissions of the user running Excel.
The vulnerability exists due to a heap-based buffer overflow in Microsoft Office Excel when processing a specially crafted workbook during formula entry. A remote attacker can send a specially crafted Excel workbook and convince a user to open it for editing and begin typing a formula to execute arbitrary code with that user's permissions.
The Preview Pane is not an attack vector for this vulnerability.
Affected software
Microsoft Office for macOS
Microsoft Office
Office Online Server
Microsoft Office
Office Online Server
How to mitigate CVE-2026-118721
Install security update from vendor's website.
Microsoft Office for macOS - update to 16.115.26110837
Office Online Server - update to 16.0.10417.20236
Microsoft Office - addressed in versions 16.0.14334.21048, 16.0.17932.21140
Office Online Server - update to 16.0.10417.20236
Microsoft Office - addressed in versions 16.0.14334.21048, 16.0.17932.21140