I set up a Minikube-Cluster with the MongoDB Community Kubernetes Operator. To view the content i want to set up a mongo-express Instance which connects to the Mongo-Cluster/ReplicaSet. But if I apply the Deployment the Container always fails with:

mongo-express_1  | Waiting for localhost:27017...
mongo-express_1  | Welcome to mongo-express
mongo-express_1  | ------------------------
mongo-express_1  | 
mongo-express_1  | 
mongo-express_1  | Mongo Express server listening at http://0.0.0.0:8081
mongo-express_1  | Server is open to allow connections from anyone (0.0.0.0)
mongo-express_1  | basicAuth credentials are "admin:pass", it is recommended you change this in your config.js!
mongo-express_1  | Database connected
mongo-express_1  | Admin Database connected
mongo-express_1  | Error [MongoError]: Authentication failed.
mongo-express_1  |     at Function.MongoError.create (/node_modules/mongodb-core/lib/error.js:31:11)
mongo-express_1  |     at /node_modules/mongodb-core/lib/connection/pool.js:483:72
mongo-express_1  |     at authenticateStragglers (/node_modules/mongodb-core/lib/connection/pool.js:429:16)
mongo-express_1  |     at Connection.messageHandler (/node_modules/mongodb-core/lib/connection/pool.js:463:5)
mongo-express_1  |     at Socket.<anonymous> (/node_modules/mongodb-core/lib/connection/connection.js:319:22)
mongo-express_1  |     at Socket.emit (events.js:314:20)
mongo-express_1  |     at addChunk (_stream_readable.js:297:12)
mongo-express_1  |     at readableAddChunk (_stream_readable.js:272:9)
mongo-express_1  |     at Socket.Readable.push (_stream_readable.js:213:10)
mongo-express_1  |     at TCP.onStreamRead (internal/stream_base_commons.js:188:23) {
mongo-express_1  |   operationTime: Timestamp { _bsontype: 'Timestamp', low_: 1, high_: 1611234788 },
mongo-express_1  |   ok: 0,
mongo-express_1  |   errmsg: 'Authentication failed.',
mongo-express_1  |   code: 18,
mongo-express_1  |   codeName: 'AuthenticationFailed',
mongo-express_1  |   '$clusterTime': {
mongo-express_1  |     clusterTime: Timestamp { _bsontype: 'Timestamp', low_: 1, high_: 1611234788 },
mongo-express_1  |     signature: { hash: [Binary], keyId: [Long] }
mongo-express_1  |   }
mongo-express_1  | }
mongo-express_1  | unable to list databases
mongo-express_1  | Error [MongoError]: command listDatabases requires authentication
mongo-express_1  |     at Function.MongoError.create (/node_modules/mongodb-core/lib/error.js:31:11)
mongo-express_1  |     at /node_modules/mongodb-core/lib/connection/pool.js:483:72
mongo-express_1  |     at authenticateStragglers (/node_modules/mongodb-core/lib/connection/pool.js:429:16)
mongo-express_1  |     at Connection.messageHandler (/node_modules/mongodb-core/lib/connection/pool.js:463:5)
mongo-express_1  |     at Socket.<anonymous> (/node_modules/mongodb-core/lib/connection/connection.js:319:22)
mongo-express_1  |     at Socket.emit (events.js:314:20)
mongo-express_1  |     at addChunk (_stream_readable.js:297:12)
mongo-express_1  |     at readableAddChunk (_stream_readable.js:272:9)
mongo-express_1  |     at Socket.Readable.push (_stream_readable.js:213:10)
mongo-express_1  |     at TCP.onStreamRead (internal/stream_base_commons.js:188:23) {
mongo-express_1  |   operationTime: Timestamp { _bsontype: 'Timestamp', low_: 1, high_: 1611234788 },
mongo-express_1  |   ok: 0,
mongo-express_1  |   errmsg: 'command listDatabases requires authentication',
mongo-express_1  |   code: 13,
mongo-express_1  |   codeName: 'Unauthorized',
mongo-express_1  |   '$clusterTime': {
mongo-express_1  |     clusterTime: Timestamp { _bsontype: 'Timestamp', low_: 1, high_: 1611234788 },
mongo-express_1  |     signature: { hash: [Binary], keyId: [Long] }
mongo-express_1  |   }
mongo-express_1  | }

For the ease of testing I used docker-compose to start mango-express and created a Port-Forwarding to access the cluster.

Versions:

• MongoDB Cluster: tried 4.2.6 and 4.4.3
• mongo-express: 0.54.0

Here the Deployment/Service I use for MongoDB Cluster creation:

---
apiVersion: mongodb.com/v1
kind: MongoDB
metadata:
  name: example-mongodb
spec:
  members: 3
  type: ReplicaSet
  version: "4.4.3"
  security:
    authentication:
      modes: ["SCRAM"]
  users:
    - name: mongoadmin
      db: admin
      passwordSecretRef: # a reference to the secret that will be used to generate the user's password
        name: mongoadmin-password
      roles:
        - name: root
          db: admin
      scramCredentialsSecretName: my-scram

# the user credentials will be generated from this secret
# once the credentials are generated, this secret is no longer required
---
apiVersion: v1
kind: Secret
metadata:
  name: mongoadmin-password
type: Opaque
stringData:
  password: mongoadmin                                 

And here the compose-file i use for mongo-express:

version: '3.8'

services:
  mongo-express:
    image: mongo-express
    restart: on-failure
    ports:
      - 8081:8081
    network_mode: host
    environment:
      ME_CONFIG_MONGODB_SERVER: localhost
      ME_CONFIG_MONGODB_ADMINUSERNAME: mongoadmin
      ME_CONFIG_MONGODB_ADMINPASSWORD: mongoadmin

The thing is, that if I setup up a mongo (4.4.3) container with mongo-express via docker-compose everything works fine...

Does anybody have a clue whats going on?