A newly disclosed Linux kernel vulnerability, CVE-2026-53359, dubbed Januscape, has exposed a critical weakness in the Linux Kernel-based Virtual Machine (KVM) hypervisor. The flaw resides in the shadow MMU code and allows attackers to escape a virtual machine (VM), compromise the underlying host, and potentially execute arbitrary code. 

Security researchers warn that the issue poses a serious risk to multi-tenant x86 public cloud environments running untrusted guests with nested virtualization enabled. 
Januscape Flaw Affects KVM Shadow MMU Code 

Discovered by security researcher Hyunwoo Kim (@v4bel), CVE-2026-53359 is described as a use-after-free vulnerability in the KVM/x86 shadow ...