PyCharm cannot clone GitHub repositories when using an HTTP proxy in a network without a default route

Product: PyCharm
Version: 2026.3
Operating System: Windows 11

Description
I installed PyCharm today and encountered an issue when trying to clone GitHub repositories.
Cloning any GitHub repository via HTTPS fails with the following error:

Network Environment
Our department operates in a highly secured network environment:

• There is no direct Internet access.
• There is no Internet router and no default route configured.
• All external communication must go through an HTTP/HTTPS proxy server.
• The proxy is configured in PyCharm and the built-in connection test succeeds.
• A test connection to https://example.com works correctly.
• Immediately after installation, PyCharm was able to download and install updates through the configured proxy.

This indicates that the proxy configuration is generally working.

Additional Observations

• The internal DNS server can resolve github.com successfully using: nslookup github.com
• However, commands such as Ping and tracert fail with messages similar to:  Unable to resolve target system name github.com which is expected in our environment due to the missing default route.
• GitHub repositories can be accessed and downloaded successfully using standard web browsers configured with the same proxy. 
• Installing Python packages from within PyCharm also works correctly.
• Only the GitHub clone operation fails.
• The repository URL used is the HTTPS URL.  SSH and GitHub CLI are not involved.

Thank you for your support.
Arno