Azure Cloud Shell and Container Instances breakout
Published Mon, Feb 15th, 2021
An attacker could gain root privileges on their Azure Cloud Shell container,
escape from the container, and then gain root privileges on the underlying node,
the root cause being an insecure kubelet port (10250), among other cluster misconfigurations.
Once they could access the node filesystem, an attacker could extract kubelet API
credentials which allowed listing all pods and nodes in the cluster, including
those belonging to other tenants. Moreover, an attacker could bypass RBAC policies
in the cluster by deploying a pod with the "NodeSelector" flag, and thereby escalate
their privileges to root on other tenants' containers (the same issue affected
Azure Container Instances).