CTF Challenges

Hack Acid Reloaded VM (CTF Challenge)

The named of the Virtual machine is “Acid-Reloaded”, It is created by Avinash Thappa. This Virtual Machine contains both network logics and web logics. You will need to extract the RAR and run the vmx using VMplayer. The machine has DHCP active list so once automatically assign an IP network, the next step will be to identify the target and discover the / the service / s to start the game.

GOAL: Escalate the privileges to the root user and capture the flag. Once anyone able to beat the box then shoots me a mail

Penetrating Methodologies

  • Network scanning (netdiscover, nmap)
  • Port knocking (Netcat)
  • Abusing HTTP web service (Brupsuite)
  • SQL injection (Sqlmap)
  • SSH Brute-Force (Hydra)
  • Access PTY shell (ssh login)
  • Kernel privilege escalation

Let’s Begin!!

As always start by finding our target


This tells us that our target is Now is time to scan with nmap.

nmap -A

The result of nmap shows us that only port 22 is open with the service of SSH. Let’s check out this 22 port.


Wann Knock me out??? Sounds like port knocking hint, therefore, let’s go for port knocking.

Checking out port 22 hints (3.2.1 let’s Start the Game) we will use the netcat Port Knocking technique.

nc 3
nc 2
nc 1

Let’s scan with nmap again.

nmap -p- -A

Port knocking helped us to open port 33447 on which the service of HTTP was redirected.

Now open the target IP on the browser using this port.

A simple webpage opens that tells us to use our brain. Haha! Even the page source did not help. It’s time to use dirb for a directory brute-force attack.


It put-up so many web directories but to me /bin/ might be interesting as it might have a shell system. No harm in checking it out in browsing so let’s do that.

And it’s a login portal. Now let’s check its page source.

In the page source, there is a directory called: includes/validation.php. I decided to check it out.

Unfortunately! I could not find anything on it. So decided to use DirBuster to find out about directories.

In the DirBuster give the URL and for wordlist use medium 1.0-word list. And then click on the Start button and it will start finding directories. So it found so many PHP files as shown below.

I checked every directory related to the bin and only /bin/dashboard.php was useful. When I opened it in the browser, I found nothing useful so I looked into the page source and even that proved to be non-useful.

When nothing helped I decided to capture its cookies using BurpSuite. To capture the cookies using BurpSuite, set proxy and then turn on the interception and then simply reload the page. When the cookies are captured just add the following below the Host.

Referer :

And now as soon as you will hit the forward button it will automatically log in.

On the page it says to click and when you do that it will redirect to the following page.

There was nothing on the redirected page or its page source. So decided to check for SQL injection, and search for a web page with id=1. Luckily we have made the right prediction and got the following result for id=1.

Using a single quote () I check for SQL injection and got MySQL error message which means the web application is vulnerable to SQL injection.

So decided to use SQLMap.

sqlmap -u --dbs --tamper=space2comment --batch

We got database name secure_login, now let’s find out tables.

sqlmap -u -D secure_login --table --tamper=space2comment

It shows us the name of the table i.e. UB3R/strcpy.exe

When I opened /UB3R/strcpy.exe in the browser, a dialogue box opened and asked to save a file and so I did.

Now use the file command to know more it and found PDF document V 1.5, then used the foremost tool which is a forensic tool which is used to recover files using their headers and footers.

file strcpy.exe
foremost strcpy.exe

As soon as you will run the above command a folder is created with the name of output. Let’s check out this folder.

cd output

There is a text file in the folder with the name of an audit, I decided to read it through cat command.

cat audit.txt

There is a .rar which I decided to unrar.

unrar x 00000213.rar

On unzipping there are two files that have been extracted i.e. acid.txt and lol.jpg. I decided to read acid.txt

cat acid.txt

This .txt tells us that we are on the right path. So of course next I opened lol.jpg

exiftool lol.jpg

But found nothing. So I unzipped it.

unrar e lol.jpg

Unzipping the lol.jpg gave me two files again, one was “hint.txt” and another “Avinash.contact”. So I opened hint.txt which told me to go with Avinash.contact, so I next opened.

cat hint.txt
cat Avinash.contact

There was a base64 code given in the file so we decoded the base64 code with help of echo as shown and it turned to be NooB@123.

Syntax: echo Base64 text | base64 -d

And then applied brute force on SSH using the text file that I just created with random words. With help of the following command, we try to crack the password for SSH and successfully obtained two credential for SSH login.

hydra -L user.txt -p NooB@123 -u ssh

And it gave us makke: NooB@123 as username and password respectively. And so I logged in with SSH.

ssh makke@

Give the password when asked. And when I logged in I checked kernel’s version and tried to download its exploit but it didn’t happen. All the options for downloading were blocked so started exploring.

So I directly went for the/bin.

cd /bin

In the/bin, there were files called overlayfs. This is a famous exploit so I executed it

ls –la

And then, fortunately, there was a flag.txt.

cat flag.txt

AuthorYashika Dhir is a passionate Researcher and Technical Writer at Hacking Articles. She is a hacking enthusiast. contact here