Firefox - Secure Connection Failed

Secure Connection Failed

An error occurred during a connection to SSL received a malformed Server Hello handshake message. Error code: SSL_ERROR_RX_MALFORMED_SERVER_HELLO

The page you are trying to view cannot be shown because the authenticity of the received data could not be verified.

Wut, is the cyber police gonna catch me?
The root domain (, without "catalog.") was using an expired SSL certificate. It's fixed now.

This normally didn't affect the catalog subdomain (
I still get this error. Do I have to clean something? Clearing cache doesn't help.
>Do I have to clean something?
History -> Show All History -> search for -> right click on a page -> Forget About This Site.
This will clear all your filters and settings though.

But try in incognito or in another browser first, just in case.
It happens to me on several computers, doesn't seem to be some local data problem, but it only happens in Firefox.
I looked into Wireshark and compared the handshakes with of Firefox and Chromium. I noticed that Firefox's handshake is listed as TLSv1.3 in the protocol column, while Chromium's is labeled as TLSv1.2. I disabled TLSv1.3 in Firefox by setting security.tls.version.max in about:config to 3. Now it works in Firefox.
So I guess there is a bug in the TLSv1.3 implementation of Firefox or's server.
Confirm about FF
The default is 4 in the latest Firefox.
You must have some kind of very outdated version.
I think you misunderstood. I set it from the default (which is indeed 4) to 3. If it's set to 4 TLSv1.3 is enabled, if it's set to 3 it's disabled and the catalog is working.
OP here,I changed the security.tls.version.fallback-limit to 3 and then back to 4 and it works. Also there was a firefox update when I restarted ff.