See Mortgagee Letter 2015-17
If buyers overbid and want to use FHA financing, as of the effective date they will not be required to bring the amount of the overbid in the form of cash to closing. However, if the property appraises for less than the purchase price, buyers may still be required to bring cash to closing. If Selling Agents or buyers have questions they should contact their lender and reference this mortgagee letter.
Below is a link to the complete mortgagee letter:
http://portal.hud.gov/hudportal/documents/huddoc?id=15-17ml.pdf