There are a few ways to reset the password on an individual account … but they require you to have a known password. But what about when you don’t have any good passwords? (You might be able to read your kibana.yml and get a known good password, so that would be a good place to check). Provided you have OS access, just create another superuser account using the elasticsearch-users binary:

/usr/share/elasticsearch/bin/elasticsearch-users useradd ljradmin -p S0m3pA5sw0Rd -r superuser

You can then use curl to the ElasticSearch API to reset the elastic account password

curl -s --user ljradmin:S0m3pA5sw0Rd -XPUT "http://127.0.0.1:9200/_xpack/security/user/elastic/_password" -H 'Content-Type: application/json' -d'
{
"password" : "N3wPa5sw0Rd4ElasticU53r"
}
'