1. Begin by performing a comprehensive network scan to discover all services running on the target system:

nmap -Pn -sS -sV -p- <target-ip>

2. The scan reveals two open ports:

• Port 80: Running nginx web server
• Port 8080: Running Jetty (Java-based web server), which is commonly used by Jenkins

3. Perform more detailed scans on the discovered ports:

nmap -Pn -sS -sV -p 80,8080 --script=http-title,http-headers <target-ip>

4. Key discovery: Port 8080 is running Jenkins version 2.387.3

1. Examine the nginx service on port 80:

curl -I http://<target-ip>:80

2. Access the web page to see the challenge description:

curl http://<target-ip>:80

3. Investigate the Jenkins service on port 8080:

curl -I http://<target-ip>:8080

4. Critical discovery: Jenkins is accessible without authentication, indicating a security misconfiguration

1. Navigate to the Jenkins dashboard in your browser:

http://<target-ip>:8080

2. Security issue: Jenkins is running without authentication enabled, which is a critical misconfiguration
3. On the Jenkins dashboard, you'll see a job named "BuildMe"
4. Click on the BuildMe job and then click Configure to examine the build configuration
5. Critical discovery: The build script contains cat /flag.txt, which will output the flag when the job is executed

1. Since Jenkins is unsecured, you can trigger the build job to execute the shell command:

• Click on the BuildMe job
• Click Build Now to trigger a new build
• Wait for the build to complete (it should finish quickly)

2. Once the build completes:

• Click on the build number (e.g., #1) in the build history
• Click Console Output to view the build logs

3. Flag found in the console output:

Started by user anonymous
Building in workspace /var/jenkins_home/workspace/BuildMe
[BuildMe] $ /bin/sh -xe /tmp/jenkins1234567890.sh
+ cat /flag.txt
fe35b52a-165b-4067-8aaa-ddef7d068ed4
Finished: SUCCESS

4. Flag Found: fe35b52a-165b-4067-8aaa-ddef7d068ed4

1. Direct file access (if available):

curl http://<target-ip>:8080/flag.txt

2. Jenkins Script Console (if you have administrative access):

println new File('/flag.txt').text

• Unsecured Jenkins: Running Jenkins without authentication is a critical security vulnerability
• Arbitrary Code Execution: The ability to execute shell commands through build jobs can lead to full system compromise
• Privilege Escalation: Jenkins typically runs with elevated privileges, making this vulnerability even more dangerous
• Data Exposure: Sensitive files and system information can be accessed through build scripts

This type of misconfiguration is commonly found in real-world environments and has led to numerous security breaches:

• Code Repository Access: Attackers can clone private repositories and steal intellectual property
• Credential Theft: Access to environment variables and stored credentials
• Infrastructure Compromise: Ability to deploy malicious code or access other systems
• Data Breaches: Access to sensitive data and configuration files

This challenge demonstrates a realistic attack scenario involving:

1. Network reconnaissance to identify Jenkins services
2. Discovery of security misconfigurations (unsecured Jenkins)
3. Exploitation of CI/CD automation for command execution
4. Flag extraction through build job execution
5. Understanding of real-world DevOps security risks