This is going to be an in-depth explaination of the overlapping chunks techniques on GLIBC 2.27, this technique can also be produced on the GLIBC 2.23 but for this blog, I did a challenge from HITCON CTF 2018 which seemed very interesting in itself. I loved this challenges as I learned a lot about heap internals and how the heap really recycles the chunk and how prev_size plays a big role here.