The Zapscape vulnerability (CVE-2026-64561), discovered by Hyunwoo Kim, allows a guest to escape to the host in a KVM/x86 environment, executing commands with root privilege. This use-after-free vulnerability resides in KVM's shadow MMU emulation, specifically in the recursive zap path. It can be triggered by guest-side actions alone, corrupting the host kernel's shadow page and threatening guest-host isolation in environments accepting untrusted guests or offering nested virtualization.

The Proof of Concept (PoC) targets AMD systems and is recommended to be run under QEMU TCG. It involves a multi-layered guest setup (L0, L1, L2) where memory touches in L2 trigger KVM's quota reclaim, leading to a use-after-free bug in L0. While the PoC is demonstration code and not a weaponized exploit for cloud environments, porting it is described as not difficult.

Zapscape affects versions from 2020-07-08 to 2026-07-21. Its impact is similar to Januscape (CVE-2026-53359), enabling KVM escape for host compromise or privilege escalation. The vulnerability occurs in in-kernel KVM, independent of QEMU, and requires root privilege within the guest VM to exploit.