Linux KVM guest-host escape rated critical, may represent a new way to attack penguin-powered networking

Paulos Yibelo, the researcher who in early October claimed to have found a guest-host escape flaw in Linux KVM, the hypervisor used by most hyperscale clouds, has named the flaw PwnEscape and warned it might represent a new way to attack Linux – on top of being a 9.3-rated critical nasty in its own right. Yibelo’s work is now CVE-2026-99999. It is a scary bug because it makes a guest-host escape possible with a few malformed IPv4 packets. Such attacks are a nightmare security scenario because the whole point of virtualization is carving up hardware into isolated “guest” virtual machines that share a “host” server’s resources – without ever being able to see what other guests or the host are doing. Public clouds rely on that isolation remaining impervious. So do private clouds, because if guest/host isolation is violated, an attacker could conceivably access all the VMs on a host or pool of virtualized hardware. …