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Error Unknown Host

Rahul | Last updated: Mar 08, 2024 08:28AM UTC

Issue: Always getting Error Unknown Host regardless of website visited in Burp Browser. Trying to load lab Detail: I am attempting to connect as I did the day prior, on the same connection. Again, this has worked without issues or modifications for two days in a row. Today, no matter what I do, I am getting Error Unknown Host. Note that in my Internet Options in Control Panel on Windows, in the Connections tab, after clicking LAN settings, I have "Use a proxy server for your LAN checked". However, as stated above, I was able to successfully intercept requests on lab pages two days in a row. This is not the case now. Now, for whatever reason, that first page that normally pops up when you open Burp Browser is not there. Also, I have Googled this issue. I found results like https://www.youtube.com/watch?v=AX5iLrUbjoU. They get exceedingly complicated, especially seeing as I don't believe I modified anything. I've tried adding the proxy and the port that my Wifi is working on into Proxy Settings in Burp but after clicking "Regenerate CA certificate" it tells me I have to install the CA certificate in the browser. Even if I wanted to install the CA certificate in my Chrome browser, it isn't immediately clear where the path to the certificate is. I checked the appdata folder and there's nothing obvious. Can anyone help? I also uninstalled Burp Suite and then re-installed it (but without touching the appdata folder). The startup page on Burp Browser remained gone and the error "unknown host" continued when trying to access the lab page. I then deleted the Burp Suite folder in appdata and did a fresh install of burpsuite_community_windows-x64_v2024_1_1_4.exe . This brought back the Burp Browser start page but unfortunately I'm still getting the unknown host error for labs that load fine in Chrome (the labs always load fine in Chrome). I then took a look at Proxy Settings in Burp Suite again, and it's what was there when I first checked after getting the issue (127.0.0.1:8080) Note that I've tried adding the specific address and port I am using in internet options, and that did not work (although I didn't get past "regenerate CA certificate") I've tried keeping both checked in Proxy Server settings, and each one individually. Nothing works. Any ideas? Note that I'm loading these as temporary projects in memory and using burp defaults.

Michelle, PortSwigger Agent | Last updated: Mar 08, 2024 10:50AM UTC

Hi Are all sites affected, or just certain ones? Can you access the labs successfully using your normal browser, which is not proxied via Burp? If so, can you please confirm whether or not your normal browser is configured to use a proxy server? If it is, make a note these settings and then add them in Burp under Settings > Network > Connections > Upstream proxy servers. You can then test accessing the site using Burp's embedded browser (Proxy > Intercept > open browser). If you use Burp's embedded browser, you do not need to worry about importing Burp's CA certificate or about configuring your browser to use Burp.

Rahul | Last updated: Mar 08, 2024 08:32PM UTC

Your change worked! Thank you so so much! Specifically, I added ip and port to Upstream proxy servers. Other: Before I tried your Upstream proxy server fix, normal websites like google.com or duckduckgo.com were not working on Burp Browser. However, I had not tried them in Burp Browser before I started having issues. I had not made any changes to Chrome in order to run it through the proxy server. I simply check "Use a proxy server for your LAN". And yes, I could access the labs successfully in my normal browser. Extra: I got "Failed to connect to (proxy ip):(port)" after I tried to go back to normal Wifi. I fixed this by unchecking the recently added rule.

Rahul | Last updated: Mar 08, 2024 08:36PM UTC

When I mention "Use a proxy server for your LAN", I mean the Windows setting, not Chrome. Thanks!

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