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A screenshot of a computer Description automatically generated

A screenshot of a computer screen Description automatically generated

Most likely vulnerability: Perform a SSRF attack against App01.example.com from CDN.example.com.

The scenario suggests that the CDN network (with a WAF) can be used to perform a Server-Side Request Forgery (SSRF) attack. Since the penetration tester has the pentester workstation interacting through the CDN/WAF and the production network is behind it, the most plausible attack vector is to exploit SSRF to interact with the internal services like App01.example.com.

Two best remediation options:

Restrict direct communications to App01.example.com to only approved components.

Require an additional authentication header value between CDN.example.com and App01.example.com.

Restrict direct communications to App01.example.com to only approved components: This limits the exposure of the application server by ensuring that only specified, trusted entities can communicate with it.

Require an additional authentication header value between CDN.example.com and App01.example.com: Adding an authentication layer between the CDN and the app server helps ensure that requests are legitimate and originate from trusted sources, mitigating SSRF and other indirect attack vectors.

Nmap Scan Observations:

CDN/WAF shows open ports for HTTP and HTTPS but filtered for MySQL, indicating it acts as a filtering layer.

App Server has open ports for HTTP, HTTPS, and filtered for MySQL.

DB Server has all ports filtered, typical for a database server that should not be directly accessible.

These findings align with the SSRF vulnerability and the appropriate remediation steps to enhance the security of internal communications.

Based on the Nmap scan results, the services identified on the target server are as follows:

22/tcp open ssh:

Service: SSH (Secure Shell)

Function: Provides encrypted remote access.

Attack Surface: Brute force attacks or exploiting vulnerabilities in outdated SSH implementations. However, it is generally considered secure if properly configured.

25/tcp filtered smtp:

Service: SMTP (Simple Mail Transfer Protocol)

Function: Email transmission.

Attack Surface: Potential for email-related attacks such as spoofing, but the port is filtered, indicating that access may be restricted or protected by a firewall.

111/tcp open rpcbind:

Service: RPCBind (Remote Procedure Call Bind)

Function: Helps in mapping RPC program numbers to network addresses.

Attack Surface: Can be exploited in specific configurations, but generally not a primary target compared to others.

2049/tcp open nfs:

Service: NFS (Network File System)

Function: Allows for file sharing over a network.

Attack Surface: NFS can be a significant target for attacks due to potential misconfigurations that can allow unauthorized access to file shares or exploitation of vulnerabilities in NFS services.

Conclusion: The NFS service (2049/tcp) provides the best target for launching an attack. File sharing services like NFS often contain sensitive data and can be vulnerable to misconfigurations that allow unauthorized access or privilege escalation.

When a penetration tester identifies email addresses during reconnaissance, the most immediate risk to leverage for an attack is unauthorized access to the network. Here’s why:

Phishing Attacks:

Email addresses are often used to conduct phishing attacks. By crafting a convincing email, an attacker can trick the recipient into revealing their login credentials or downloading malicious software, thereby gaining unauthorized access to the network.

Spear Phishing:

With specific email addresses (like admin@acme.com), attackers can perform spear phishing, targeting key individuals within the organization to gain access to more sensitive parts of the network.

Comparison with Other Risks:

Exposure of sensitive servers to the internet (B): This is unrelated to the email addresses and more about network configuration.

Likelihood of SQL injection attacks (C): SQL injection targets web applications and databases, not email addresses.

Indication of a data breach in the company (D): The presence of email addresses alone does not indicate a data breach.

Email addresses are a starting point for phishing attacks, making unauthorized access to the network the most relevant risk.

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The key detail in the Nmap scan output is that port 2222/tcp is open and running the SSH service. The standard SSH port is 22, so if the tester was attempting to connect on port 22, they would not succeed because SSH is instead listening on port 2222.

This is a common security hardening tactic—moving services to non-standard ports to reduce automated attacks.

There is no indication that the service is blocked (B), or requires certificates (C), or is inactive (D), because Nmap clearly shows the service is open and identified.

CompTIA PenTest+ Reference:

PT0-003 Objective 3.3: Analyze tool output or data related to engagement activities.

Nmap usage and interpreting scan results is emphasized in multiple sections.