Heap-based buffer overflow in Microsoft products - CVE-2026-118299
Published: November 11, 2026
Vulnerability identifier: #VU165095
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-2026-118299
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 victim user's privileges.
The vulnerability exists due to a heap-based buffer overflow in Microsoft Office Excel when applying AutoFormat to cells in a specially crafted spreadsheet. A remote attacker can convince a user to open the spreadsheet and apply AutoFormat to its cells to execute arbitrary code with that user's privileges.
Affected software
Microsoft Office for macOS
Microsoft Office
Office Online Server
Microsoft Office
Office Online Server
How to mitigate CVE-2026-118299
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