Can I Receive Communion If My First Husband Dies?

The Church presumes the first exchange of vows is valid unless proven otherwise (canon 1060). That would mean that without an annulment a divorced person is not free to remarry and any subsequent exchange of vows would be invalid. Marriage, however, is “until death do us part” and therefore the marriage bond ceases with the death of the spouse.

In the situation you describe, while the second exchange of vows is not valid, upon the death of the first spouse you would be free to remarry. In order to receive communion you would first need to validate your current civil marriage in the Church.