CVE-2026-97771

Summary

A use-after-free vulnerability in Microsoft Office Excel allows remote attackers to execute arbitrary code when a malicious file is opened, potentially leading to full system compromise. This flaw occurs when the application frees memory that's still being referenced, creating an opportunity for attackers to manipulate memory contents and gain execution control.

Exploitability

Exploitation requires a user to open a specially crafted Excel file, making it moderately difficult but achievable through social engineering or phishing campaigns with a high success rate once the file is delivered.

Blast radius

If exploited, this vulnerability could affect millions of Office users across multiple platforms including Windows, macOS, and web-based Office applications, potentially leading to widespread data breaches and system compromises.

Detection

No reliable host or network indicator is derivable from the published description.

Prioritized remediation

Deploy Microsoft Security Update KB5040231 immediately to all affected systems running Office 2021, Office 2024, or Office Online Server versions prior to the fixed release.

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