You are quite right. The Qur'an confirms that the Bible had been corrupted even before Prophet Muhammad's times.
2:75 Do you still hope that they will join your ranks in faith? A party among them used to listen to the Word of God in the Torah, then, distorted its words and true meanings, after they had understood it. And they knew full well what they were doing!
2:79 Then, lost are those (their scholars) who write the scripture with their own hands and then claim, “This is from God.” They traffic it for petty gains. And loss is to them for what they write, and for the illicit profits they make thereby.”
3:78 Among them is a group who distort the scripture, to make you think that what they relate is a part of the scripture, when it is not from the scripture. And they assert that it is from God, when it is not from God. Thus, they tell lies concerning God, and they are well aware of it.
3:187 God accepted a solemn pledge from those who had received the scripture, “Make it clearly known to people, and never conceal it!” But they flung it behind their backs, and traded it away for a little gain. How evil was the bargain they made!