Siberians have a strong prey drive. It was developed over thousands of years when these dogs were set free in summer to fend for themselves. Hunting meant they got to eat. In the winter they were fed for pulling sleds. For the most part anything smaller is fair game to a husky. The prey drive is part of them, just as much as pulling a sled is.
I have 3 indoor cats and they are never messed with by my dogs. My huskies came into the family as puppies and quickly learned that the cats are off-limits. However, I’m not too confident a stray cat in the backyard would fair as well.