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External proxy configuration failed

Ramón | Last updated: Apr 15, 2021 05:53PM UTC

Hello I have a problem, I am trying to do a pentest to a web app that only allows me to connect through an unauthenticated corporate proxy. I set the upstream proxy to burp, but I still can't navigate when traffic is intercepted by burp. To all this, checking the burp logs says the following: the client failed to negotiate TLS connection to https: //mytargetapp.local "Received fatal alert: unknow_ca" Burp certificates are installed in the browser

Uthman, PortSwigger Agent | Last updated: Apr 16, 2021 06:27AM UTC

Hi Ramón, If you disable TLSv1.3 on your proxy listener, does the issue persist? You can do this by selecting a proxy listener > Edit > TLS Protocols > Use custom protocols > Deselect TLSv1.3 If that does not work either, is your corporate proxy performing some type of SSL inspection? Can you provide a link to the documentation for your proxy vendor and the product?

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