Modification of Client hello TLS packet

Filip Petr. filipakanation at
Fri Sep 1 16:02:27 UTC 2023

This extension is my custom. It's the same extension that Google chrome
added ( You can check this
extension on your Chrome browser using this following URL

I don't understand why this is an issue for my Java program? I checked in
Wireshark and the hex values in this extension are exactly the same that my
browser sends out. For example, the browser sends it out like this aa aa 00
01 00 and i send it out like this 0a 0a 00 01 00. The only difference is
the first 2 bytes that are kind of random as per convention. I don't
understand why my Java doesn't like this?
Only thing I did is added the tls grase .java file inside /security/ssl
called ( with following content ( and added it inside (

I don't see why it would throw an exception?
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <>

More information about the security-dev mailing list