How to fix Flannel CNI plugin. Error: [plugin flannel does not support config version ""]

The accepted solution is incomplete and will cause headache down the line.

The proper solution to make this change permanent is to edit the ConfigMap created by flannel in your Kubernetes cluster. Otherwise, the file will be recreated the next time the flannel pod volumes are populated with the ConfigMap (e.g. on node reboot).

Use kubectl edit cm -n kube-system kube-flannel-cfg to edit the ConfigMap provided by flannel, and add the missing line:

  5 apiVersion: v1
  6 data:
  7   cni-conf.json: |
  8     {
  9       "name": "cbr0",
 10       "cniVersion": "0.2.0",
 11       "plugins": [

Reboot the node, or alternatively make the change manually in /etc/cni/net.d/10-flannel.conflist and do systemctl restart kubelet afterwards to skip the reboot.

The file /etc/cni/net.d/10-flannel.conflist was missing cniVersion key in its config.

Adding "cniVersion": "0.2.0" solved the issue.