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Client Failed to negotiate a TLS Connection to respective application

ReddyChalla, | Last updated: Jan 06, 2020 01:30PM UTC

Hello BurpSuite Support, When I was trying to test a web application using Burp Suite 2.1.07 it is showing with an error Client failed to negotiate a TLS Connection to www.xxxxxxx.com: Received fatal alert:_certificate unknown. Steps followed on my side: Installed Burp CA Cert in Chrome browser, IE, Firefox—still shows up with same error. 2. Tried to change settings in Project Options> TLS—Still DIDN’T WORK. We had an implementation this week. Can you please help us in troubleshooting this issue. Thanks, Satya.

Hannah, PortSwigger Agent | Last updated: Jan 06, 2020 02:08PM UTC

Hi Satya Have you tried deleting and reinstalling the Burp certificate? Could you also tell me your OS, your Java version, whether you are using Professional or Community, and if you are using the platform installer or the plain .JAR file?

Burp User | Last updated: Jan 06, 2020 03:52PM UTC

Hi Jan, Yeah i have installed cert twice. I am using Windows 10 Machine to run the scans.I am using Professional version. Thanks, Satya.

Burp User | Last updated: Jan 06, 2020 04:03PM UTC

Hi Jan, I have Java 8 Update 231 on my machine. Thanks, Satya.

Hannah, PortSwigger Agent | Last updated: Jan 07, 2020 09:40AM UTC

Hi Satya Are you using the platform installer version or the plain .JAR file? Could you try running Burp using a different Java version?

Burp User | Last updated: Jan 07, 2020 12:43PM UTC

Hi, It is a platform installer. In Past i used previous version of 2.1.07. It worked fine without any issue. Thanks, Satya.

Ben, PortSwigger Agent | Last updated: Jan 07, 2020 01:03PM UTC

Hi Satya, Just to confirm, is this behavior common across all sites or just the particular one that you are currently testing? If it is just one site, is the site public facing and are you able to send us details so that we can investigate from our side (if you want to send us an email with the details then please feel free)? You also say that you have used previous versions of Burp and it worked fine - do you mean that Burp has worked previously against the site you are having issues with now or that it worked fine in general?

Liam, PortSwigger Agent | Last updated: Jan 07, 2020 01:30PM UTC

Support is provided via email only. When you have used previous versions of Burp and it worked fine – do you mean that Burp has worked previously against the site you are having issues with now or that it worked fine in general? Would it be possible to send a screenshot of the error message to support@portswigger.net?

Burp User | Last updated: Jan 07, 2020 03:05PM UTC

I have used Burp for the same Application and it went find in the month of november. It is a internal website. Can we schedule a call to resolve this issue. Thanks, Satya.

Burp User | Last updated: Jan 07, 2020 04:45PM UTC

With previous versions of Burp for the site am working on ran the scan without any issues. For the latest version of version of Burp, facing this issue. I just want to make sure whether latest version is causing this issue. I will take the screenshot and update to you. Thanks, Satya.

Burp User | Last updated: Jan 07, 2020 09:23PM UTC

Emailed the screenshot showing error message to support@portswigger.net

Ben, PortSwigger Agent | Last updated: Jan 08, 2020 08:16AM UTC

Thank you Satya. We will get back to you via your email.

Ben, PortSwigger Agent | Last updated: Jan 08, 2020 10:45AM UTC

Hi Max, If you have a particular issue then please feel free to email support@portswigger.net. The nature of these issues means that some of the details may not be suitable for sharing on a public forum, hence why we request that we are contacted via email.

Burp User | Last updated: Jan 22, 2020 10:03AM UTC

And where is solution?

Burp User | Last updated: Jan 26, 2020 08:26AM UTC

Hi this issue occurs, in my company site. On desember working, but know i got same error

Ben, PortSwigger Agent | Last updated: Jan 27, 2020 08:28AM UTC

Hi, Are you able to provide us with some further details? What version of Burp are you using and what error messages are you seeing? Also, are you able to tell us the URL of the site that you are having trouble with and is it a public facing website?

Meghana | Last updated: Jun 07, 2022 10:36AM UTC

Hi Team, We are facing this error "Client failed to negotiate a TLS Connection to www.xxxxxxx.com: Received fatal alert:_certificate unknown". while accessing the Api's even though we have installed the latest Burp certificate. Team please assist!

Ben, PortSwigger Agent | Last updated: Jun 08, 2022 09:57AM UTC

Hi Meghana, I have just replied to your email about this issue - it might be easier, in terms of information sharing, to discuss this via that medium.

Meghana | Last updated: Jun 09, 2022 06:47AM UTC

Yes, I received the mail and shared the details with you. Kindly assist!

Raji | Last updated: Jul 11, 2023 11:06AM UTC

Hi Team, We are facing this error "Client failed to negotiate a TLS Connection to www.xxxxxxx.com: Received fatal alert:_certificate unknown". while accessing the Api's even though we have installed the latest Burp certificate. Team please assist!

Ben, PortSwigger Agent | Last updated: Jul 12, 2023 08:10AM UTC

Hi Raji, I can see that you are already talking to one of my colleagues about this issue in a separate email that you have sent us. Keeping to one communication method is going to lead to us better dealing with your issue so please continue your discussions via the email chain.

gaibu | Last updated: Aug 21, 2023 01:38PM UTC

Hi Team, We are facing this error "Client failed to negotiate a TLS Connection to www.xxxxxxx.com: Received fatal alert:_certificate unknown". Please assist

Dominyque, PortSwigger Agent | Last updated: Aug 21, 2023 01:53PM UTC

Hi Can you please email support@portswigger.net with the following: 1) Could you send me your diagnostics information? You can find this by going to "Help > Diagnostics" within Burp. 2) Can you please take a screenshot of the Event Log (with the debug filter enabled)?

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