CVE intelligence

CVE-2026-66809

Vulnerability intelligence

Published Aug 11, 2026Sources checked Oct 28, 2026

5.5MEDIUMCVSS out of 10

What this means

Review the available evidence

CVE-2026-66809 and is rated Medium severity with a CVSS score of 5.5. It is not in the current CISA KEV record we collected. That does not prove exploitation has not occurred.

What to do next

Remediation and response

Microsoft Security Response Center guidance

Vendor revision: Sep 17, 2026

Click to Run Release Notes Install KB5002901.

Vendor-listed releases

https://aka.ms/OfficeSecurityReleases
16.112.26081010
16.0.5565.1000

CISA KEVNot listedBased on the latest collected catalog

EPSS0.4%Estimated 30-day exploitation probability

Ransomware useNot markedCISA KEV ransomware field

Threat actors0Source-linked actor relationships

Overview

What is CVE-2026-66809?

Out-of-bounds read in Microsoft Office allows an unauthorized attacker to disclose information locally.

Source: NVD