🔴 Critical | Source: Microsoft Security Response Center
CVE-2026-47243 is a critical vulnerability in the Kata Containers runtime-rs implementation that allows an attacker with root access inside a Kata guest VM to escape the container sandbox and gain root-level access on the underlying host via the virtiofs filesystem sharing mechanism. This is a full container escape, bypassing the hardware virtualisation boundary that Kata Containers is specifically designed to enforce. It is particularly significant for Azure customers using confidential or sandboxed container workloads where strong isolation guarantees are assumed.
Security Architect’s Take: Identify any Azure Kubernetes Service (AKS) or container workloads using Kata Containers with the runtime-rs shim and virtiofs enabled, and apply available patches or mitigations immediately — this breaks the core isolation guarantee of Kata. If patching is not yet possible, consider switching to an alternative storage backend (e.g. virtio-blk) or temporarily falling back to a standard runc runtime while assessing exposure.
Original advisory: CVE-2026-47243 Kata guest escape: runtime-rs guest-root to host-root escape via virtiofs