When the entity (in the US, typically a county sheriff or designee) auctions a foreclosed property the noteholder may set the starting price as the remaining balance on the mortgage loan. However, there are a number of issues that affect how pricing for properties is considered, including bankruptcy rulings. In a weak market the foreclosing party may set the starting price at a lower amount if it believes the real estate securing the loan is worth less than the remaining principal of the loan.
In the case where the remaining mortgage balance is higher than the actual home value the foreclosing party is unlikely to attract auction bids at this price level. A house that went through a foreclosure auction and failed to attract any acceptable bids may remain the property of the owner of the mortgage. That inventory is called REO (real estate owned). In these situations the owner/servicer will try to sell it through standard real estate channels.