Same Problem here with 6.0.1, proxy on server without user and pass.

From the amount and level of information you have provided it is really impossible to provide any help or assistance. Please provide as much detail as possible about your proxy and its configuration settings.

Summary

I am experiencing an issue with Joomla 6 where core updates work correctly, but extension update checks fail when the site is behind an HTTP proxy.

I am not an expert on this topic, but I tried to gather as much relevant technical information as possible.

Environment

• Joomla version: 6.0.1
• PHP version: 8.3 (PHP-FPM)
• Operating system: Debian 12
• Web server: Apache with PHP-FPM
• Database: MariaDB 10.11
• Proxy type: HTTP forward proxy
  • No authentication (username and password are empty)
  • Configured in Joomla (proxy host and port only)
• PHP configuration:
  • allow_url_fopen = Off

Observed behaviour

• Joomla core updates are fetched successfully and show no errors.
• Extension update checks fail with the error message:
  Could not open update site

This occurs consistently for multiple third-party extensions.

Proxy and network verification

To verify that the proxy and network configuration are working correctly, I performed the following tests via SSH on the same server.

CLI curl test via proxy

curl -Iv -x http://proxy:3128 https://cdn.akeeba.com/updates/pkgakeebabackuppro.xml

Result: successful response.

PHP cURL test via proxy

php -r '
$ch = curl_init("https://cdn.akeeba.com/updates/pkgakeebabackuppro.xml");
curl_setopt($ch, CURLOPT_PROXY, "proxy:3128");
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, true);
var_dump(curl_exec($ch) !== false);
'

Result: true.

Logs

I checked the Joomla log directory, but no log entries are written when this issue occurs.
It appears that the request fails before anything is logged.

Additional notes

Given that:

• Joomla core updates work
• CLI curl via proxy works
• PHP cURL via proxy works
• allow_url_fopen is disabled

it appears that in Joomla 6 the proxy configuration may not be consistently applied to the HTTP requests used for extension update checks.

The same proxy setup worked correctly with latest Joomla 5 on the same infrastructure. The HTTP transport selection option was already removed in Joomla 5, but extension update checks still worked there. The issue only appeared after upgrading to Joomla 6.

Thank you very much for your time and support — I hope this helps.