16-Year-Old Linux KVM Flaw Lets Guest VMs Escape to Host on Intel and AMD x86 Systems
Jul 06, 2026
Linux / Vulnerability
A use-after-free bug in Linux's KVM hypervisor can be triggered from a guest virtual machine to corrupt the shadow-page state of the host kernel that runs it. Dubbed ' Januscape ' and tracked as CVE-2026-53359 , the flaw sits in the shadow MMU code that KVM shares across both Intel and AMD. The public proof-of-concept panics the host; the researcher claims that a separate, unreleased exploit turns the same bug into full host code execution. Security researcher Hyunwoo Kim (@v4bel) found and reported the bug. He described Januscape as the first guest-to-host exploit triggerable on both Intel and AMD, to the best of public knowledge. The flaw went unnoticed for roughly 16 years. According to Kim, the exploit was used as a zero-day submission in Google's kvmCTF , the controlled KVM vulnerability reward program that offers up to $250,000 for full guest-to-host escapes. How It Works To run a virtual machine, KVM keeps its own private set of page tables that mi...
