SSL: error:1425F102:SSL routines:ssl_choose_client_version:unsupported protocol

Symptoms

Unable to reverse proxy a web application.

A 502 HTTP status code is returned instead.

In the log files, a similar error can be seen:

2023-09-07 11:44:17.988059+00:00 awingu nginx.service[<unknown>:838348]: awingu nginx: 2023/09/07 11:44:17 [error] 838348#838348: *331763 SSL_do_handshake() failed (SSL: error:1425F102:SSL routines:ssl_choose_client_version:unsupported protocol) while SSL handshaking to upstream, client: 1.2.3.4, server: somehostheader.org, request: "GET / HTTP/1.1", upstream: "https://10.33.10.46:443/", host: "somehostheader.org"
2023-09-07 11:44:17.988470+00:00 awingu nginx.service[<unknown>:838348]: awingu nginx:  - somehostheader.org -  - - [07/Sep/2023:11:44:17 +0000] "GET / HTTP/1.1" 502 564 "-" "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/116.0.0.0 Safari/537.36" 4.267 1.036

Cause

The web application relies on an outdated TLS version.

Current product versions only support TLS 1.2.

Resolution