That MIGHT be a juvenile. Juvenile cardinals of either sex tend to be a uniform grayish-brown all aver with a dark gray or black bill. Male Cardinals vary a LOT on the amount of red. Also, the time of year can have an influence on the amount of red. In late Summer, many Cardinals, male and female, go COMPLETELY bald with NO feathers on their head. They have plenty of feathers elsewhere on their bodies, just none on their head.
JUVENILE NORTHERN CARDINAL
BALD FEMALE NORTHERN CARDINAL