title: kubectl exec fails "cannot validate certificate because it doesn't contain any IP SANs"
body: <p>I'm trying to use kubectl exec to enter one of my containers, but I'm getting stuck on this error.</p>
  
  <pre><code>$ kubectl exec -it ubuntu -- bash
  error: Unable to upgrade connection: {
      "kind": "Status",
      "apiVersion": "v1",
      "metadata": {},
      "status": "Failure",
      "message": "x509: cannot validate certificate for &lt;worker_node_ip&gt; because it doesn't contain any IP SANs",
      "code": 500
  }
  </code></pre>
  
  <p>I have configured kubectl with my CA certificate and admin keys, etc according to this guide <a href="https://coreos.com/kubernetes/docs/1.0.6/configure-kubectl.html" rel="noreferrer">https://coreos.com/kubernetes/docs/1.0.6/configure-kubectl.html</a></p>
  
  <h2>Update</h2>
  
  <p>I also found the same error in the API server's logs</p>
  
  <pre><code>E1125 17:33:16.308389 1 errors.go:62] apiserver received an error that is not an unversioned.Status: x509: cannot validate certificate for &lt;worker_node_ip&gt; because it doesn't contain any IP SANs
  </code></pre>
  
  <p>Does this mean I have configured the certs incorrectly on my worker/master nodes or on kubectl on my local machine?</p>