The information in this document focuses primarily on cloud based deployments. For on-premise deployments, additional security work that is specific to your installation method would also be required. Note that your specific installation’s security needs might be more or less stringent than what we can offer you here.

Brad Geesamen gave a wonderful talk titled Hacking and Hardening Kubernetes by Example at Kubecon NA 2017 and you can watch the talk. Highly recommended that you do so to understand the security issues you are up against when using Kubernetes to run JupyterHub.

Reporting a security issue#

If you find a security vulnerability in JupyterHub, either a failure of the code to properly implement the model described here, or a failure of the model itself, please report it to

If you prefer to encrypt your security reports, you can use this PGP public key.


This section describes how to enable HTTPS on your JupyterHub. The easiest way to do so is by using Let’s Encrypt, though we’ll also cover how to set up your own HTTPS credentials. For more information on HTTPS security see the certificates section of this blog post.

Set up your domain#

  1. Buy a domain name from a registrar. Pick whichever one you want.

  2. Create an A record from the domain you want to use, pointing to the EXTERNAL-IP of the proxy-public service. The exact way to do this will depend on the DNS provider that you’re using.

  3. Wait for the change to propagate. Propagation can take several minutes to several hours. Wait until you can type in the name of the domain you bought and it shows you the JupyterHub landing page.

    It is important that you wait - prematurely going to the next step might cause problems!

Set up automatic HTTPS#

JupyterHub uses Let’s Encrypt to automatically create HTTPS certificates for your deployment. This will cause your HTTPS certificate to automatically renew every few months. To enable this, make the following changes to your config.yaml file:

  1. Specify the two bits of information that we need to automatically provision HTTPS certificates - your domain name & a contact email address.

        enabled: true
          - <your-domain-name>
          contactEmail: <your-email-address>
  2. Apply the config changes by running helm upgrade ...

  3. Wait for about a minute, now your hub should be HTTPS enabled!


If the proxy service is of type LoadBalancer, which it is by default, then a specific static IP address can be requested (if available) instead of a dynamically acquired one. Although not essential for HTTPS, using a static IP address is a recommended practice for domain names referencing fixed IPs. This ensures the same IP address for multiple deployments. The IP can be provided like:


More info about this can be found on the Configuration Reference page.

Set up manual HTTPS#

If you have your own HTTPS certificates & want to use those instead of the automatically provisioned Let’s Encrypt ones, that’s also possible. Note that this is considered an advanced option, so we recommend not doing it unless you have good reasons.

There are two ways to specify your manual certificate, directly in the config.yaml or by creating a Kubernetes secret.

Specify certificate in config.yaml#

  1. Add your domain name & HTTPS certificate info to your config.yaml

        enabled: true
        type: manual
          key: |
            -----BEGIN RSA PRIVATE KEY-----
            -----END RSA PRIVATE KEY-----
          cert: |
            -----BEGIN CERTIFICATE-----
            -----END CERTIFICATE-----
  2. Apply the config changes by running helm upgrade ….

  3. Wait for about a minute, now your hub should be HTTPS enabled!

Specify certificate through Secret resource#

  1. Create a secret resource with type containing your certificate.

    kubectl create secret tls example-tls --key="tls.key" --cert="tls.crt"

  2. Add your domain and the name of your secret to your config.yaml.

        enabled: true
          - <your-domain-name>
        type: secret
          name: example-tls
  3. Apply the config changes by running helm upgrade ….

  4. Wait for about a minute, now your hub should be HTTPS enabled!

Off-loading SSL to a Load Balancer#

In some environments with a trusted network, you may want to terminate SSL at a load balancer. If https is enabled, and proxy.https.type is set to offload, the HTTP and HTTPS front ends target the HTTP port from JupyterHub.

The HTTPS listener on the load balancer will need to be configured based on the provider. If you’re using AWS and a certificate provided by their certificate manager, your config.yml might look something like:

    enabled: true
    type: offload
      # Certificate ARN "arn:aws:acm:us-east-1:1234567891011:certificate/uuid"
      # The protocol to use on the backend, we use TCP since we're using websockets "tcp"
      # Which ports should use SSL "https" "3600"

Annotation options will vary by provider.

Confirm that your domain is running HTTPS#

There are many ways to confirm that a domain is running trusted HTTPS certificates. One options is to use the Qualys SSL Labs security report generator. Use the following URL structure to test your domain:<YOUR-DOMAIN>

Minimal hub image#

The default hub image includes some useful debugging tools. You can use the slim version of image to minimise your exposure to vulnerabilities in those optional tools.

    # The slim variant excludes a few non-essential packages that are useful
    # when debugging something from the hub pod. To use it, apply this
    # configuration.


We are based on Linux Debian as a base image. There are container scanners that pick up known vulnerabilities in Debian that the Debian security team has dismissed. For details about this, see this comment.

Secure access to Helm#

Helm 3 supports the security, identity, and authorization features of modern Kubernetes. Helm’s permissions are evaluated using your kubeconfig file. Cluster administrators can restrict user permissions at whatever granularity they see fit.

Read more about organizing cluster access using kubeconfig files in the Kubernetes docs.

Delete the Kubernetes Dashboard#

The Kubernetes Dashboard gets created by default in many installations. Although the Dashboard contains useful information, the Dashboard also poses a security risk. We recommend deleting it and not using it for the time being until the Dashboard becomes properly securable.

You can mitigate this by deleting the Kubernetes Dashboard deployment from your cluster. This can be most likely performed with:

kubectl --namespace=kube-system delete deployment kubernetes-dashboard

In older clusters, you might have to do:

kubectl --namespace=kube-system delete rc kubernetes-dashboard

Use Role Based Access Control (RBAC)#

Kubernetes supports, and often requires, using Role Based Access Control (RBAC) to secure which pods / users can perform what kinds of actions on the cluster. RBAC rules can be set to provide users with minimal necessary access based on their administrative needs.

It is critical to understand that if RBAC is disabled, all pods are given root equivalent permission on the Kubernetes cluster and all the nodes in it. This opens up very bad vulnerabilities for your security.

As of the Helm chart v0.5 used with JupyterHub and BinderHub, the helm chart can natively work with RBAC enabled clusters. To provide sensible security defaults, we ship appropriate minimal RBAC rules for the various components we use. We highly recommend using these minimal or more restrictive RBAC rules.

If you want to disable the RBAC rules, for whatever reason, you can do so with the following snippet in your config.yaml:

  create: false

We strongly discourage disabling the RBAC rules and remind you that this action will open up security vulnerabilities. However, some cloud providers may not support RBAC in which case you can disable it with this config.

Kubernetes API Access#

Allowing direct user access to the Kubernetes API can be dangerous. It allows users to grant themselves more privileges, access other users’ content without permission, run (unprofitable) bitcoin mining operations & various other not-legitimate activities. By default, we do not allow access to the service account credentials needed to access the Kubernetes API from user servers for this reason.

If you want to (carefully!) give access to the Kubernetes API to your users, you can do so with the following in your config.yaml:

  serviceAccountName: <service-account-name>

You can either manually create a service account for use by your users and specify the name of that here (recommended) or use default to give them access to the default service account for the namespace. You should ideally also (manually) set up RBAC rules for this service account to specify what permissions users will have.

This is a sensitive security issue (similar to writing sudo rules in a traditional computing environment), so be very careful.

There’s ongoing work on making this easier!

Audit Cloud Metadata server access#

Most cloud providers have a static IP that pods can reach to get metadata about the cloud. This metadata can contain very sensitive info and in the wrong hands allow attackers to take full control of your cluster and cloud resources. Due to this, it is critical to secure the metadata service from your user pods that could end up running malicious code without knowing it.

This presentation, 27 min in and onwards, provides more information on the dangers presented by this attack.

This Helm chart blocks access to this metadata in two ways by default, but you only need one.

Block cloud metadata API with a NetworkPolicy enforced by a NetworkPolicy controller#

If you have NetworkPolicy controller such as Calico or Cilium in the Kubernetes cluster, it will enforce the NetworkPolicy resource created by this chart (singleuser.networkPolicy.*) that by default doesn’t allow (and therefore blocks) user access to the cloud metadata API exposed on a specific IP (


If you have a NetworkPolicy controller, we recommend relying on it and setting singleuser.cloudMetadata.blockWithIptables to false.

Block cloud metadata API with a privileged initContainer running iptables#

If you can’t rely on the NetworkPolicy approach to block access to the cloud metadata API, we suggest relying on this option instead. When singleuser.cloudMetadata.blockWithIptables is true as it is by default, an initContainer is added to the user pods. It will run with elevated privileges and use the iptables command line tool to block all network access to the cloud metadata server.

# default configuration
    blockWithIptables: true

Changed in version 3.0.0: This configuration is not allowed to be configured true at the same time as singleuser.networkPolicy.egressAllowRules.cloudMetadataServer to avoid an ambiguous configuration.

Kubernetes Network Policies#


Your Kubernetes cluster may silently ignore the network rules described in the NetworkPolicy resources that this Helm chart can create. NetworkPolicy rules are enforced by an optional NetworkPolicy controller that often isn’t setup as part of setting up a Kubernetes cluster.

By default this Helm chart creates four different NetworkPolicy resources describing what incoming/ingress and outgoing/egress connections are to be allowed for the pods they target.

A critical point to understand is that if a pod’s ingress or egress connections respectively aren’t targeted by a NetworkPolicy, they won’t be constrained by them at all. If they are though, only what is explicitly allowed for them will be accepted. In other words, the act of defining a NetworkPolicy targeting a pod is what is constraining it, but all the rules in the NetworkPolicy are allow rules.

Introduction to the chart’s four network policies#

The four network policies declare rules for four kinds of pods created by the Helm chart. Below are some tables describing what the four network policy do to some extent.


Associated Helm chart config

Influenced pods

Notable software in pods




jupyterhub, kubespawner, jupyterhub-idle-culler, Authenticator








traefik, lego






Always allowed outbound connections (egress) for core functionality


To proxy pod’s REST API port (8001), user pods’ only port (8888)


To hub pod’s only port (8081), user pods’ only port (8888)


To proxy pod’s http proxy port (8000)


To hub pod’s only port (8081), proxy pod’s proxy port (8000), autohttps pod’s http (8080) and https (8443)


Always allowed inbound connections (ingress) for core functionality, ingress is allowed for specific ports from pods with certain labels


From pods labelled


From pods labelled (http proxy port) or (REST API port) in the same namespace


From pods labelled (http(s) proxy ports)


From pods labelled (notebook-port)


Not all functionality summarized above It has been tricky to document the full behavior of these network policies. For in depth details, please for now refer to inspecting the Helm chart’s templates and the rendered result given your configuration.

Below are links to the Helm chart’s templates.

Below are commands you can use to render the specific template.

# These four commands renders the four NetworkPolicy resource templates of the
# latest release of the JupyterHub Helm chart, with default values.
# You can pass `--values <your config file>` or `--version <version here>` to
# these commands to inspect the rendered NetworkPolicy resources given your
# specific version and configuration.
helm template --repo jupyterhub --show-only templates/hub/netpol.yaml
helm template --repo jupyterhub --show-only templates/proxy/netpol.yaml
helm template --repo jupyterhub --show-only templates/proxy/autohttps/netpol.yaml
helm template --repo jupyterhub --show-only templates/singleuser/netpol.yaml

Enabling and disabling network policies#

NetworkPolicy resources are created by default, and with their creation they restrict inbound and outbound network connections to those explicitly allowed in the NetworkPolicy resource. To opt-out of creating NetworkPolicy resources, use configuration like below.

# Example configuration on how to disable the creation of all the Helm chart's
# NetworkPolicy resources.
    enabled: false
      enabled: false
      enabled: false
    enabled: false

Allowing additional inbound network connections (ingress)#

While you can add allow arbitrary allow rules with the <hub|proxy.chp|proxy.traefik|singleuser>.networkPolicy.ingress configuration besides the rules ensuring core functionality, you can also label the pods you want to be allowed to establish connections to the Helm chart’s various pods.

For example, to access the hub pod from another pod in the same namespace, just add the label "true" to the pod that should be able to establish a connection to the hub pod.

The available access labels are:

  • "true", access the hub api

  • "true", access proxy public http endpoint

  • "true", access proxy api

  • "true", access singleuser servers directly

If you wish to access the pod from another namespace with these labels, then read about <hub|proxy.chp|proxy.traefik|singleuser>.networkPolicy.interNamespaceAccessLabels.

Finally, the option <hub|proxy.chp|proxy.traefik|singleuser>.networkPolicy.allowedIngressPorts enable you to allow incoming connections on certain pods.

Allowing additional outbound network connections (egress)#

While you can add allow arbitrary allow rules with the <hub|proxy.chp|proxy.traefik|singleuser>.networkPolicy.egress configuration besides the rules ensuring core functionality, you can also toggle some pre-defined allow rules on or off. They are documented in the configuration reference under <hub|proxy.chp|proxy.traefik|singleuser>.networkPolicy.egressAllowRules.

By default, all egress allow rules are enabled for hub, proxy.chp, and proxy.traefik, but singleuser.networkPolicy.egressAllowRules.cloudMetadataServer and singleuser.networkPolicy.egressAllowRules.privateIPs default to false. In practice, this can mean no rule allows the user pods to communicate with some k8s local service with Private IPv4 addresses.

Changed in version 2.0.0: Before JupyterHub Helm chart 2.0.0 the default configuration was to allow singleuser pods to establish outbound connections to anything. After 2.0.0 singleuser.networkPolicy.egressAllowRules.privateIPs=true must be explicitly set for this.

Restricting Load Balancer Access#

By default any IP address can access your JupyterHub deployment through the load balancer service. In case you want to restrict which IP addresses are allowed to access the load balancer, you can specify a list of IP CIDR addresses in your config.yaml as follows:


This would restrict the access to only two IP addresses: and