Heap-based buffer overflow in Microsoft products - CVE-2026-58618
Published: July 17, 2026
Vulnerability identifier: #VU138184
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-2026-58618
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.
The vulnerability exists due to heap-based buffer overflow in Microsoft Office Excel when parsing a crafted Office file. A remote attacker can send a specially crafted file to a victim and convince them to open it to execute arbitrary code.
User interaction is required to open the crafted file, and the Preview Pane is not an attack vector.
Affected software
Microsoft Office for macOS
Microsoft Excel
Office Online Server
Microsoft Excel
Office Online Server
How to mitigate CVE-2026-58618
Install security update from vendor's website.
Microsoft Office for macOS - update to 16.111.26071215
Microsoft Excel - update to 16.0.5561.1001
Office Online Server - update to 16.0.10417.20175
Microsoft Excel - update to 16.0.5561.1001
Office Online Server - update to 16.0.10417.20175