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VNC Exploitation / Pentest Approach

I just wana ask you guys, what are your approach when it comes to VNC ports? Example , port 5800 and 5900 and so on.
I usually try for default creds and brute force with a small vnc default word lists. That's about it. Don't really dig much into it.
[Image: j90qyxk.gif]
Anyone have specific and interesting approach here?
[Image: j90qyxk.gif]
(Nov 30, 2021 04:55 AM)Money- Wrote:  Anyone have specific and interesting approach here?

I don't know if this will help you, but here is my approach I use to work a bit on the topic for a company.

This is what I've done for my audit:

1) What do you target? A company.
2) How do they integrate their VNC servers on their devices?
- Manual Install ?
- Using Integration servers with Pre-packaged software, in my use case they used script. Scripts may still be on the computer in the /Temp/ repository. You'll be surprised toto the see the amount of sensitive information you could find.

--> First, you need to identify the VNC server used
Usually if the VNC port 5900/5800 is open. You can type on your Web Browser the target address: https://127.0.0.1:5900
It should disclose the version of the VNC server.
I was able to find a miss configuration in the integration scripts which allowed me to connect remotely to a generically session without the user knowing.

--> Check for default credentials/bruteforcing

--> If you want to train :

--> Check the vulnerabilities associated with the VNC server used: https://www.cvedetails.com/cve/CVE-2021-42785/, for instance on tightvnc (23 November) --> Write your own exploit or find them on the web.

Hope I helped, xx
Don't hesitate to reach out for security services
(Dec 7, 2021 07:56 AM)Dolla$ Wrote:  I don't know if this will help you, but here is my approach I use to work a bit on the topic for a company.

This is what I've done for my audit:

1) What do you target? A company.
2) How do they integrate their VNC servers on their devices?
- Manual Install ?
- Using Integration servers with Pre-packaged software, in my use case they used script. Scripts may still be on the computer in the /Temp/ repository. You'll be surprised toto the see the amount of sensitive information you could find.

--> First, you need to identify the VNC server used
Usually if the VNC port 5900/5800 is open. You can type on your Web Browser the target address: https://127.0.0.1:5900
It should disclose the version of the VNC server.
I was able to find a miss configuration in the integration scripts which allowed me to connect remotely to a generically session without the user knowing.

--> Check for default credentials/bruteforcing

--> If you want to train :

--> Check the vulnerabilities associated with the VNC server used:      https://www.cvedetails.com/cve/CVE-2021-42785/, for instance on tightvnc (23 November) --> Write your own exploit or find them on the web.

Hope I helped, xx


Thanks for the info , most of the time when I browse the webpage it doesn't disclose any information and gives error or a blank page from my pentest experience anyways.

I usually will just nmap it for the version instead. So far default credentials seem to work but meh.
[Image: j90qyxk.gif]
There are a few nmap scripts to query the version, look on official nmap site for the NSE you want.

nmap -p 5901 --script vnc-info ipaddress

From here check exploit dB for a way in.

On one of my pen tests I found the vnc password hash in the config file in program files on a windoze box. Vncpwd.exe cracked it in less than 2 secs. This password was also used for local admin. Always worth having a look around on the system that winpeas / seatbelt missed.
(Jan 19, 2022 06:22 AM)ice_c00l Wrote:  There are a few nmap scripts to query the version, look on official nmap site for the NSE you want.

nmap -p 5901 --script vnc-info ipaddress

From here check exploit dB for a way in.

On one of my pen tests I found the vnc password hash in the config file in program files on a windoze box. Vncpwd.exe cracked it in less than 2 secs. This password was also used for local admin. Always worth having a look around on the system that winpeas / seatbelt missed.

Yea I am using that, usually there isn't much stuff on my end though. When it comes to the version.
Though I did found some default credentials for VNC before which is interesting.

If you got anymore info about VNCs , let me know. Thanks!
[Image: j90qyxk.gif]
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