CVE-2026-47243

Received Received - Intake

Guest-Root to Host-Root Escape in Kata Containers

Publication date: 2026-08-07

Last updated on: 2026-08-07

Assigner: GitHub, Inc.

Description

Kata Containers is an open source project focusing on a standard implementation of lightweight Virtual Machines (VMs) that perform like containers. Prior to 3.31.0, the runtime-rs standalone virtio-fs path is vulnerable to a guest-root to host-root escape. In this configuration, Kata runs the host virtiofsd as root with --sandbox none --seccomp none, so an attacker with root-equivalent access inside the guest can bypass the guest virtio-fs client entirely by taking over the virtio-fs PCI device and building a virtqueue in userspace to submit raw FUSE requests directly to the host virtiofsd. A crafted FUSE_SYMLINK request whose new symlink name is an absolute host path is honored outside the configured shared directory, allowing guest root to create root-owned symlinks in sensitive host locations such as /etc/cron.d. By pointing such a symlink at a guest-controlled crontab payload reachable through a live runtime process's mount namespace, the attacker causes the host cron daemon to execute that payload as host root, crossing the Kata isolation boundary. This issue is fixed in version 3.31.0.

CVSS Scores

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Meta Information

Published

2026-08-07

Last Modified

2026-08-07

Generated

2026-08-08

AI Q&A

2026-08-08

EPSS Evaluated

N/A

NVD

CVE-2026-47243

Affected Vendors & Products

Vendor	Product	Version / Range
kata_containers	kata_containers	to 3.31.0 (exc)

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-22	The product uses external input to construct a pathname that is intended to identify a file or directory that is located underneath a restricted parent directory, but the product does not properly neutralize special elements within the pathname that can cause the pathname to resolve to a location that is outside of the restricted directory.
CWE-36	The product uses external input to construct a pathname that should be within a restricted directory, but it does not properly neutralize absolute path sequences such as "/abs/path" that can resolve to a location that is outside of that directory.

Attack-Flow Graph

Executive Summary

Kata Containers prior to 3.31.0 has a flaw in its virtio-fs implementation. When configured with runtime-rs standalone virtio-fs, the host virtiofsd runs as root without sandboxing or seccomp restrictions. An attacker with root-equivalent access inside a guest VM can exploit this by taking control of the virtio-fs PCI device and submitting raw FUSE requests directly to the host. This allows creating symlinks outside the shared directory, potentially pointing to malicious payloads that execute as host root when processed by the cron daemon.

Detection Guidance

This vulnerability can be detected by checking the Kata Containers version. If your system is running a version prior to 3.31.0, it is vulnerable. Run: kata-runtime --version to check the installed version.

Impact Analysis

If you use Kata Containers versions before 3.31.0 with virtio-fs enabled, an attacker with root access in a guest VM could escape isolation and gain full root access on the host system. This could lead to complete system compromise, data theft, or further network infiltration.

Compliance Impact

This vulnerability severely impacts compliance by breaking isolation boundaries between guest and host systems. It could lead to unauthorized access to sensitive data, violating GDPR's data protection principles or HIPAA's security requirements for protected health information.

Mitigation Strategies

Upgrade Kata Containers to version 3.31.0 or later to address the vulnerability. If upgrading is not immediately possible, avoid using the runtime-rs standalone virtio-fs path with the vulnerable configuration (running host virtiofsd as root with --sandbox none --seccomp none).

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