In `AsisCTF Quals 2018 - Message Me!` challenge, we leak `libc` base address using a `Use After Free (UAF)` vulnerability. Using the same `Use After Free (UAF)` vulnerability, we overwrite `__malloc_hook` by `overlapping fastbin chunks`. Finally, we trigger `__malloc_hook` using a `Double Free` vulnerability on `fastbins`. This is a good example of `Heap Exploitation` challenge to understand how to hijack control flow in `x86_64` binaries with `Canary`, `NX`, and `ASLR` enabled.