CVE-2026-69910

CVE-2026-69910 is a critical stack-based buffer overflow (CWE-121) in Windows Hyper-V that Microsoft rates 9.8 on the CVSS 3.1 scale. It is triggered when an unauthenticated remote attacker sends crafted input over a network to a vulnerable Hyper-V component, overflowing a stack-based buffer. Successful exploitation could allow the attacker to execute arbitrary code with high impact on confidentiality, integrity, and availability (per the CVSS scope). Any Windows deployment with Hyper-V enabled is potentially affected; the available data does not specify affected version ranges, so defenders should consult Microsoft's advisory. There is no public proof-of-concept, the flaw is not yet in CISA's KEV catalog, and EPSS puts 30-day exploitation probability at about 1%, indicating no known exploitation to date.

What to do: Apply Microsoft's security update for CVE-2026-69910 via Windows Update/WSUS as soon as it is released, prioritizing multi-tenant and network-exposed Hyper-V hosts. As an interim measure, restrict network access to Hyper-V hosts and limit untrusted guest-to-host and external network paths. Inventory which servers and workstations have the Hyper-V role/feature enabled and monitor Microsoft's advisory for the confirmed affected version ranges.