kube-hunter/docs/_kb/KHV047.md

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KHV047	Pod With Mount To /var/log	Privilege Escalation

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Issue description

Kubernetes uses /var/log/pods on nodes to store Pods log files. When running kubectl logs the kubelet is fetching the pod logs from that directory. If a container has write access to /var/log it can create arbitrary files, or symlink to other files on the host. Those would be read by the kubelet when a user executes kubectl logs.

Remediation

Consider disallowing running as root: Using Kubernetes Pod Security Policies with MustRunAsNonRoot policy.
Aqua users can use a Runtime Policy with Volume Blacklist.

Consider disallowing writable host mounts to /var/log: Using Kubernetes Pod Security Policies with AllowedHostPaths policy.
Aqua users can use a Runtime Policy with Blacklisted OS Users and Groups.

References

• Kubernetes Pod Escape Using Log Mounts
• Pod Security Policies - Volumes and file systems
• Pod Security Policies - Users and groups