Looking for real-world Linux userland exploitation targets to practice on (moving beyond CTFs)

Hi all - I've been doing `pwn`/ `binary exploitation` in CTFs for about 1.5 years and want to level up by practicing on real-world targets instead of CTF challs. I'm currently focused on Linux userland exploitation. Could anyone recommend good old real-world targets or software to practice on? I'm especially looking for CVEs that are reproducible...