The Bible says that Christ is the only way of salvation. Biblical Protestant convictions have always been that no sinner can be saved apart from the saving work of Christ granted to him through faith. Christ's word, "No one comes to the Father except through Me," means that those only who are united to Christ will be saved; all others will die in their sins and suffer the wrath of God in hell forever.
The Catholic church teaches that only through faith in Christ plus Catholic baptism is salvation granted. There are exceptions; e.g., in the cases of martyrs for the faith (Catechism 1258), and infants dying without baptism (Catechism 1261).
The Second Vatican Council's Decree on Ecumenism states:
"For it is through Christ's Catholic Church ALONE, which is the universal help toward salvation, that the fullness of the means of salvation can be obtained" (emphasis added).