I was given the [binary](https://github.com/mar232320/ctf-writeups/raw/main/nactf/2022/gets) and it's [source code](https://github.com/mar232320/ctf-writeups/raw/main/nactf/2022/gets.c)
In there there is the vulnerable gets() function and a variable magic I had to overflow. ascii reprezentation of 42 is * .
The buffer of char input is 16, char takes 8 bytes itself and int 4 bytes so the overflow value must be 28. My payload was a*28 + *Sending it gave me the flag
# nactf{buff3r_0v3rfl0w_b3g1nn1ngs}