I stumbled upon kidnapped Beden in an Ashland yurt and paid 5 gold for his ransom and I was told to report to Sarano in Ald'ruhn. However, I'm not a member of Redoran house and I can't converse with Sarano about topic "Beden Giladren". What can I do?

I remember that there's a similar quest for House Hlaalu where you can solve a murder of Ralen Hlaalo despite not being a member of the house and they properly reward you.

If nothing can be done, is there some console fix?
Thanks!

Try this in the console;

AddTopic "beden giladren"

Doesn't help.

That's odd. I can't think of any reason why it wouldn't unless it's a mod conflict.

If you would like to be rid of this then try;

Journal hr_findGiladren 100
"beden giladren"-> disable