CVE-2026-102858

Summary

A heap-based buffer overflow in Microsoft Office OneNote allows remote attackers to execute arbitrary code when processing specially crafted files. This vulnerability is particularly concerning because it affects widely used Office applications and can be exploited over a network without user interaction.

Exploitability

Exploitation is moderately difficult as it requires an attacker to deliver a malicious OneNote file to a target, but the attack vector is relatively straightforward with no user interaction required once the file is opened.

Blast radius

The impact could be significant across organizations using Microsoft 365, Office 2021, and Office 2024, as these applications are commonly used for document sharing and collaboration, potentially allowing attackers to gain full system access on affected machines.

Detection

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

Prioritized remediation

Deploy the Microsoft Office 2021 or Office 2024 update KB5039876 which addresses this heap-based buffer overflow vulnerability in OneNote.

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