SSL_ERROR_UNSUPPORTED_VERSION

Shown on the "Secure Connection Failed" page as "Error code: SSL_ERROR_UNSUPPORTED_VERSION", with a note that the website might not support TLS 1.2. Locally, a TLS 1.0-only OpenSSL server made Firefox report SSL_ERROR_UNKNOWN instead in our test; the badssl host gives the specific code.

Firefox — "Secure Connection Failed": the server only supports TLS versions Firefox no longer allows

What it means

The server answered with a TLS version below Firefox's minimum (TLS 1.2), so Firefox stops with "Secure Connection Failed" and the code SSL_ERROR_UNSUPPORTED_VERSION. The site needs TLS 1.2 or 1.3; nothing is wrong with its certificate.

Why it happens

• The server supports only TLS 1.0 or 1.1

  common

  Firefox disabled TLS 1.0 and 1.1 by default in 2020 (version 78).

• Embedded admin interfaces

  occasional

  Printers, switches and UPS management cards are the most common remaining TLS 1.0 servers.

How to fix it

1. 1.

   Site owners: enable TLS 1.2 and 1.3

   Update the server or put a modern reverse proxy in front of it.

   # Site owners: enable TLS 1.2 and 1.3
   ssl_protocols TLSv1.2 TLSv1.3;                 # nginx
   SSLProtocol -all +TLSv1.2 +TLSv1.3             # Apache httpd

2. 2.

   Legacy devices: isolate rather than weaken the browser

   Lowering security.tls.version.min affects every site; if you must, do it in a separate profile and revert it.

   Old device you cannot update (printer, switch, UPS): reach its admin page only from a trusted
   management network. Firefox's "Enable TLS 1.0 and 1.1" button on the error page (setting
   security.tls.version.min) lowers protection for every site; revert it right after use.

← Browse the full signature error database