There’s no liaison between étudiant and actif, and neither between actif and étranger (where do you get that from?). There’s always a liaison after un though.

So it’s:

Un-né-tu-dian-ac-tif-é-tran-gé

And I don’t think there’s ever a liaison after curieux.

Rule of thumb of the comments, condensed:

Generally, in a sentence with [article]+[noun]+[adjective], there’s a liaison on the noun, but not on the adjective after the noun.

Ex:

Des zhistoires ( )étranges

Whereas in [article]+[adjective]+[noun], there is a liaison both on the adjective and on the noun.

Des zétranges zhistoires

Of course, this applies only if the words can have a liaison. There’s no liaison in “Un grand bûcheron” for example.

Depending on which one is the noun and which one is the adjective, the liaison might be done or not:

Un curieux (z) étranger: A curious foreigner (liaison possible but optional)

Un curieux étranger: A foreign onlooker (forbidden liaison because curieux is singular)

Un étudiant curieux étranger and étudiant actif étranger are not very idiomatic. We’d rather say either:

Un étudiant étranger curieux / Un étudiant étranger actif

or

Un curieux étudiant étranger.