Finally rooted. Didn’t feel like an ‘easy’ box.
PM for nudges.
Finally rooted this one! Thanks to all the folks above me for the hints. They were definitely needed. Here are some cryptic hints of my own, just in case someone finds them useful:
Foothold
Enumeration is key. Don’t trust automated tools. Have a look yourself.
User
This was by far the toughest part. Don’t be afraid of reading through long files and have a search engine handy.
Root
This is one of the only occasions where I’d actually say “RTFM”. You don’t actually need much else to figure this one out, aside from some solid lateral thinking.
Feel free to DM me if you need any nudges!
Wow this one is vulnerable af. Found lots of interesting CVE. Cant wait to bust it open. 
Well, please, give me your manual because it must be better than mine lol.
Even after HOURS of googling around to find the solution, I go back to the man page and I’m just… speechless.
Very frustrating box, far from being easy so don’t get discouraged if you struggle !
Didn’t mean to insinuate that it was straightforward. This also took me several hours of banging my head against a wall before I was able to figure it out. I just meant that I was able to figure it out mainly by just reading the man pages for the tools involved over and over again (and honestly getting kind of lucky with the assumptions I was making).
Not sure if you’ve rooted it yet or not, but feel free to DM me if you’re still running into issues.
Thank you, but I did manage to root it 
Why do I get: “Must be connected to a terminal.” when running (as suggested in all write-ups):
echo $TERM
export TERM=xterm
screen -x root/root
Must be connected to a terminal.
I managed to gain some files / passwords / configs, enumerate system services / network ports, but I’m stuck from there. could use a nudge, if anyone out there is willing? ;/
It was interesting machine, the only thing that took some time is about enum ports of some processes. that was not obvious to me, bacause of different background. After that all things was just compile and use, nothing hard.
I recommend you to do: python3 -c 'import pty;pty.spawn("/bin/bash")' first, so the subprocess will be created under a bash process, and it will be connected to a terminal.
Please obfuscate this , too revealing
You do understand this is a legacy box with write-ups on the net?
Can anyone start an instance of this machine ?
I spent a long time trying the intended exploit without success until I saw people mention in HackTheBox discord that you should use release arena.
I had been trying to launch release arena all day but got no machines available error.When it finally allowed me to boot a machine, my exploit worked fine.
Note that I had tried resetting the public non RA box and it didn’t help Just in case other people are having similar issues, try switching to release arena xD.