Hi Luke Fan, welcome to the website. ” title=”Very Happy” />
I know that during Vatican II the definition of “church” was expanded to mean everyone in the Christian body even those non-Catholic. So when we say the phrase “there is no salvation outside the Church” we mean there is no salvation without Jesus which other Christian groups do have in one way or another.
Now there are exceptions of course because there are people on this earth who never will have a chance to know Jesus and therefore God will not hold that against them.
The best I can find in the Catechism on a quick look is paragraph 161.
I will look later as well, but I think the documents of Vatican II would be a better resource than the Catechism.