Credit Score Competition Act of 2017 This bill amends the Federal National Mortgage Association Charter Act and the Federal Home Loan Mortgage Corporation Act to allow the Federal National Mortgage Association (Fannie Mae) and the Federal Home Loan Mortgage Corporation (Freddie Mac), when determining whether to purchase a residential mortgage, to consider a borrower's credit score only if certain procedural requirements are met with respect to the validation and approval of credit-scoring models. The Federal Housing Finance Agency may, by regulation, establish standards and criteria for processes used by Fannie Mae and Freddie Mac to validate and approve credit-scoring models in accordance with the bill.