How to get taxonomy list by custom post id via REST API?

I have an issue with custom post types taxonomies.

I can’t get taxonomy by the custom post id, instead I’m getting all taxonomies list, even if custom post hasn’t any taxonomy.

I tried: /wp-json/wp/v2/portfolio_tag?portfolio=2842

It works for posts: /wp-json/wp/v2/tags?post=2842, but not for custom taxonomies.

How can I get it right?

My taxonomies are exposed for the REST API.