post to /wp-json/wp/v2/media

JavaScript
curl --request POST \
--url http://www.yoursite.com/wp-json/wp/v2/media \
--header "cache-control: no-cache" \
--header "content-disposition: attachment; filename=tmp" \
--header "authorization: Basic d29yZHByZXNzOndvcmRwcmVzcw==" \
--header "content-type: image/png" \
--data-binary "@/home/web/tmp.png" \
--location
Source

Also in JavaScript: