Published Nov 10, 2026Sources checked Nov 10, 2026
9.8CRITICALCVSS out of 10
What this means
Review the available evidence
CVE-2026-66801 and is rated Critical severity with a CVSS score of 9.8. 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: Nov 10, 2026
Release Notes
Vendor-listed releases
2610
CISA KEVNot listedBased on the latest collected catalog
EPSSUnavailableNo current score collected
Ransomware useNot markedCISA KEV ransomware field
Threat actors0Source-linked actor relationships
Overview
What is CVE-2026-66801?
Heap-based buffer overflow in Xbox allows an unauthorized attacker to execute code over a network.