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FIX UNKOWN HOST

joneskla | Last updated: Jan 10, 2021 01:19PM UTC

hi, i've been having UNKOWN HOST ISSUE FOR LIKE 5MONTHS WTH?, burp works for 30mins then boom unkown host until like the next day, i tried the following, RE-INSTALLING BURP RE-INSTALLING FIREFOX TRIED 4 DIFFERENT BROWSERS RE-INSTALLED THE CERT MULTIPLE TIMES CHANGED NETWORK TRIED EVERYTHING

Ben, PortSwigger Agent | Last updated: Jan 11, 2021 09:22AM UTC

Hi, The Unknown Host error is usually indicative of Burp not being able to resolve the domain name into an IP address. To clarify, do you get this with every site that you are trying to access with Burp or just one (or a few) site in particular? In addition, are you using a LAN proxy in order to access the internet on your environment?

joneskla | Last updated: Jan 11, 2021 02:25PM UTC

I get unkown host on every website for proxy i configure it 127.0.0.1 in firefox proxy settings

Ben, PortSwigger Agent | Last updated: Jan 11, 2021 03:57PM UTC

Hi, As noted in my initial message - are you using a LAN proxy (this is separate from the Burp proxy) to access the internet in your environment (these are normally in place in corporate environments)?

joneskla | Last updated: Jan 12, 2021 01:28PM UTC

no i'm not using lan proxy i guess?

Ben, PortSwigger Agent | Last updated: Jan 13, 2021 10:42AM UTC

Hi, Are you able to connect to any sites using just the IP address? In addition, are you able to successfully perform DNS lookups on your machine to the sites that you are trying to reach?

joneskla | Last updated: Jan 18, 2021 11:29AM UTC

everything works fine, if i turn of proxy in firefox the site works well, but when i turn the proxy back on in firefox, burp will start showing unkown host

Ben, PortSwigger Agent | Last updated: Jan 19, 2021 09:12AM UTC

Hi, Are you able to send us an email at support@portswigger.net and include some screenshots of the settings that you have configured within Burp and in your proxy settings so that we can see how you have this setup?

Jack | Last updated: Apr 15, 2021 02:04PM UTC

I was wondering if you managed to resolve this issue? I have the same error. It mostly happens when i pause my VM when im AFK or overnight for example. When i get back and start up my VM i get the unkown host error. I do not use a LAN proxy. Quick fix for me is rebooting my VM, but this is pretty time consuming. Can provide screenshots if needed!

Michelle, PortSwigger Agent | Last updated: Apr 16, 2021 07:37AM UTC

Thanks for your message. Is Firefox on the same VM as Burp? Do you see the same error if you use Burp's embedded browser or browse to sites via IP address? If you can send some screenshots over to support@portswigger.net that would be great.

Michael | Last updated: Jan 19, 2022 12:49PM UTC

Same issue here, leaving this as Info for the Burp Team: I am in a VM, everything works fine. Then i pause the VM (suspended state) and come back a few days later, suddenly i get "Unknown Host" with orange Burp Banner in the Browser, no matter if i use FireFox or inbuilt browser. As sidenote; i fired up a VPN before putting machine in suspended state, maybe that messed with DNS settings somehow, haven't checked that. When using burp again though, vpn was definately off). After restarting the VM everything seems to work fine again, but would be nice if a restart wasn't necessary. Cheers.

Michelle, PortSwigger Agent | Last updated: Jan 19, 2022 01:35PM UTC

Thanks for your message. The 'Unknown Host' message does usually mean Burp has not been able to resolve the hostname to an IP address. Do you have Burp set to use any upstream proxies? When this happens are you able to use nslookup to resolve hostnames and browse to sites without using Burp from within the VM?

kashish | Last updated: Mar 20, 2023 06:14AM UTC

I am getting unknown host error in burp , when i am trying to connect to any site. I'm getting this error in the burp built in browser as well as if i try to intercept with firefox through foxy proxy and i have no upstream proxy configured. help me with this

Michelle, PortSwigger Agent | Last updated: Mar 20, 2023 07:57AM UTC

Hi Can you visit the same site from the machine where Burp is installed if you are not proxying traffic from Burp? If so, does that browser use an upstream proxy? Can the machine where Burp is installed resolve the hostname for the site you are visiting to an IP address?

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