CVE Alert: CVE-2025-55328 – Microsoft – Windows 11 Version 25H2

Risk verdict

High risk of local privilege escalation via a race condition in Hyper-V; patching should be urgent once updates are available.

Why this matters

An authenticated attacker could elevate to SYSTEM on a host or within a VM, enabling installation of persistent backdoors, data compromise, or spread to other virtualised resources. The impact is broad across host and guest environments where Hyper-V is present.

Most likely attack path

Exploitation requires local access with at least low privileges and no user interaction (PR:L, UI:N). The vulnerability arises from concurrent execution on shared Hyper-V resources, enabling a privilege escalation with full impact (C, I, A high). Because the vector is local, the attacker’s initial foothold must already exist on the host; remote or external exploitation is unlikely unless combined with another compromise or misconfiguration. Lateral movement is possible within the host and guest boundary if administrator actions are compromised.

Who is most exposed

Hosts and clusters running Hyper-V on Windows 10/11 workstations or Windows Server editions, especially in dev/test labs or production environments with administrative access to virtualization components.

Detection ideas

• Spikes or anomalies in Hyper-V worker threads and kernel memory usage.
• Kernel or hypervisor crash dumps linked to virtualization components.
• Unusual processes gaining SYSTEM privileges without justification.
• Repeated or suspicious attempts to access privileged Hyper-V resources or management interfaces.
• Unexpected VM state changes following user logon or small-time window.

Mitigation and prioritisation

• Apply Microsoft patches as soon as released; perform testing in a lab prior to production rollout; schedule a controlled reboot if required.
• If patching is pending, enforce strongest local authentication controls on hosts, restrict Hyper-V management access, segment virtualization hosts from untrusted networks, and enable strict EDR/monitoring for hypervisor activity.
• Validate backups and test recovery procedures; implement change-control for patch deployment.
• If KEV is confirmed or EPSS ≥ 0.5, treat as priority 1; otherwise treat as high-priority 2 with close monitoring.