We can easily bypass the shellcode check by putting NULL in the first byte.

[writeup](https://ptr-yudai.hatenablog.com/entry/2019/04/29/122753#Pwn-240-babyshell)

Original writeup (https://ptr-yudai.hatenablog.com/entry/2019/04/29/122753#Pwn-240-babyshell).