What is the real Jewish meaning of Jeremiah 8:8? Does it claim the Bible is corrupted?
The context of that passage does not refer to Biblical corruption. The general chapter in Jeremiah concerns God's expressed frustration at the people for not listening to Jeremiah's prophesies. It is in this context that the scriptural passage appears, which is:
Obviously, the passage shouldn't be read on its own, and reading chapters 7 and 8 clarifies the subject as rebuking the people's stubbornness for not listening to the word of God. There are many Jewish commentators on this chapter, but here is one example, from the Radak:
In summary, this has nothing to with a corrupt Bible but with a corrupt people who do not follow the Bible.