KVM vulnerabilities enable guest-to-host escapes

Security researchers have identified critical vulnerabilities in KVM (Kernel-based Virtual Machine) that allow for guest-to-host escapes, potentially granting attackers root access to host systems.

Vercel confirmed a KVM zero-day vulnerability after researcher Paulos Yibelo reported a full virtual machine escape. In response to the discovery through its bug bounty program, Vercel awarded Yibelo $50,000, the program’s maximum payment. Vercel CEO Guillermo Rauch confirmed the zero-day, noting that a technical write-up would follow.

Separately, a high-severity flaw tracked as CVE-2026-89775 has been identified in the Linux kernel for ARM64. This vulnerability involves a race condition in the KVM virtualization host extensions (VHE) path when nested virtualization is enabled. The flaw, which carries a CVSS score of 9.8, allows a guest VM to access freed host memory, enabling arbitrary host kernel memory read/write and full guest-to-host escape. Affected systems include Linux kernels on ARM64 using KVM VHE, such as RHEL 8.4 EUS. Mitigation requires applying upstream kernel patches or disabling nested virtualization.