from the Chrome Rest client make a GET request or curl -XGET 'http://localhost:9200' in console

rest client: http://localhost:9200

{    "name": "node",    "cluster_name": "elasticsearch-cluster",    "version": {        "number": "2.3.4",        "build_hash": "dcxbgvzdfbbhfxbhx",        "build_timestamp": "2016-06-30T11:24:31Z",        "build_snapshot": false,        "lucene_version": "5.5.0"    },    "tagline": "You Know, for Search"}

where number field denotes the elasticsearch version. Here elasticsearch version is 2.3.4

I would like to add which isn't mentioned in above answers.

From your kibana's dev console, hit following command:

GET /

This is similar to accessing localhost:9200 from browser.

Hope this will help someone.

You can check version of ElasticSearch by the following command. It returns some other information also:

curl -XGET 'localhost:9200'

{  "name" : "Forgotten One",  "cluster_name" : "elasticsearch",  "version" : {    "number" : "2.3.4",    "build_hash" : "e455fd0c13dceca8dbbdbb1665d068ae55dabe3f",    "build_timestamp" : "2016-06-30T11:24:31Z",    "build_snapshot" : false,    "lucene_version" : "5.5.0"  },  "tagline" : "You Know, for Search"}

Here you can see the version number: 2.3.4

Typically Kibana is installed in /opt/logstash/bin/kibana . So you can get the kibana version as follows

/opt/kibana/bin/kibana --version