CCC 841, quoting the Dogmatic Constitution on the Church, Lumen Gentium 16, from Vatican II, declared: The plan of salvation also includes those who acknowledge the Creator, in the first place amongst whom are the Muslims; these profess to hold the faith of Abraham, and together with us they adore the one, merciful God, mankind’s judge on the last day.
http://www.catholic.com/blog/tim-staples/do-muslims-worship-the-same-god-catholics-do
Next question, please.
Pope St. John Paul II strikes the balance beautifully, concisely, and without compromise between acknowledging what Muslims get right, and challenging where they go wrong, in his excellent book, Crossing the Threshhold of Hope. After pointing out that the Church has a “high regard for Muslims who worship one God, living and subsistent, merciful and omnipotent, the Creator of heaven and earth,” he then observes after reflecting on Islam and the Koran:
"Whoever knows the Old and New Testaments, and then reads the Koran, clearly sees the process by which it completely reduces Divine Revelation. It is impossible not to note the movement away from what God said about Himself, first in the Old Testament through the Prophets, and then finally in the New Testament through His Son. In Islam all the richness of God's self-revelation, which constitutes the heritage of the Old and New Testaments, has definitely been set aside. Some of the most beautiful names in the human language are given to the God of the Koran, but He is ultimately a God outside of the World, a God who is only Majesty, never Emmanuel, God-with-us. Islam is not a religion of redemption. There is no room for the Cross and the Resurrection(p. 92)."
St. John Paul first acknowledges the truth that Muslims get it right when they profess faith in one God. Then, and only then, does he point out they have it as wrong as wrong can be when it comes to what God has revealed to us in Scripture about who he is, and, I would add, what he asks of his people by way of his commandments.