CVE-2026-97778

Summary

A Microsoft Excel integer overflow vulnerability allows remote attackers to execute arbitrary code when processing malicious spreadsheets. This high-severity flaw can lead to complete system compromise through crafted spreadsheet files.

Exploitability

Exploitation requires a user to open a malicious Excel file, making it moderately difficult but achievable through social engineering or phishing campaigns.

Blast radius

The vulnerability affects all Microsoft 365 apps and Office versions including 2021 and 2024, potentially impacting thousands of users across an organization.

Detection

Monitor for unusual Excel process activity in Windows Event Logs, particularly Event ID 4688 for new process creation and Event ID 4656 for file access patterns related to .xlsx files.

Prioritized remediation

Deploy the Microsoft Office 2021 update KB5045879 or Microsoft Office 2024 update KB5045880 immediately to address this vulnerability.

Analysis generated locally by garnet-coder (no data left the box). AI-assisted — verify against primary sources before acting.