Since it looks like, here are people with interests in low level exploitation and things about it, I prepared a challenge targeting on buffer overflow vulnerability. If you'll like it
and will be sufficient interest, I will make some more with different emphasis. Okay, but back to the topic, in the link below you can download precompiled binary file.

Scenario is following:

[+] Stack smashing protection - disabled - red
[+] NX - enabled - green

Plus, make sure, you have ASLR set to 0 on your box (so ASLR disabled too for this one) and you are on 32bit system so you can enjoy it with all the trimmings.

The goal is execute arbitrary code, then post PoC and if you want, PM me your payload or exploit. I will share my in a week. Also, if you will agree, I'll post your payloads or exploits here, in case, there will some nice and different solutions, then some members can learn from it.

Link (binary) -
PHP Code:
thetechgame.org/file/er1iby

Link (source) -
PHP Code:
thetechgame.org/file/61j750
^ I separated it, in the case, you want to do it without see a source code, but feel free to compile it on your own, according to the scenario.

My PoC for now
i.imgur.com/VmA4me1.png

Have fun ^^