Januscape (CVE‑2026‑53359) lets KVM guests escape host when nested virtualization is enabled
A use‑after‑free bug in Linux KVM’s shadow MMU (CVE‑2026‑53359, “Januscape”) lets a privileged L1 guest break out to the host if nested virtualization is exposed. Ubuntu warns all releases are vulnerable and recommends disabling nested virtualization or applying upcoming kernel patches.