SSLError certificate has expired while using HTTPI

Question

I'm stuck with something I do not understand. Running either on my local instance (Mac OSX) or production server (Ubuntu 20.04+), I'm almost sure I'm not using the famous

dst root ca x3

certificate, still it does not work. Regular curl (outside of rails) gives no problem on same machine.

require 'httpi'
@endpoint  = "https://maps.mail.ru/osm/tools/overpass/api/interpreter"
r = HTTPI::Request.new(url: @endpoint, body: "")
HTTPI.post(r).body

Returns:

Traceback (most recent call last):
        2: from (irb):65
        1: from (irb):65:in `rescue in irb_binding'
HTTPI::SSLError (SSL_connect returned=1 errno=0 state=error: certificate verify failed (certificate has expired))

How can I know or get the certificate being used with Rails?

What is odd is if I do test while using

curl -Lks 'https://git.io/rg-ssl' | ruby

I got

Here's your Ruby and OpenSSL environment:

Ruby:           2.6.6p146 (2020-03-31 revision 67876) [x86_64-darwin19]
RubyGems:       3.3.5
Bundler:        2.2.32
Compiled with:  OpenSSL 1.1.1g  21 Apr 2020
Loaded version: OpenSSL 1.1.1i  8 Dec 2020
SSL_CERT_FILE:  /usr/local/etc/[email protected]/cert.pem
SSL_CERT_DIR:   /usr/local/etc/[email protected]/certs

With that out of the way, let's see if you can connect to rubygems.org...

Bundler connection to rubygems.org:       success ✅
RubyGems connection to rubygems.org:      success ✅
Ruby net/http connection to rubygems.org: success ✅

Hooray! This Ruby can connect to rubygems.org. You are all set to use Bundler and RubyGems. 👌

So obviously, Rails is using something else