The vulnerability arises from the Git.polish_url() method's default behavior of expanding environment variables in URLs (expand_vars=True). While the prior fix disabled this expansion for Repo.clone_from(), it did not update Repo.create_remote() or Remote.add(), which still expand variables in attacker-controlled URLs. An attacker can supply a URL containing environment variable references (e.g., ${AWS_SECRET_ACCESS_KEY}), which are expanded on the server side and stored in the repository's .git/config file. Subsequent fetch or pull operations transmit the expanded secret to the attacker's server. The check for unsafe protocols occurs after expansion and does not block HTTPS URLs carrying secrets. This issue affects GitPython versions before 3.1.55.

Sensitive environment variables from the hosting process can be exposed to an attacker by embedding them in URLs passed to Repo.create_remote() or Remote.add(). These secrets are written into the repository configuration and transmitted over the network during Git fetch or pull operations, leading to confidentiality breaches. There is no impact on integrity or availability reported.

Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Until an official fix is released, avoid using Repo.create_remote() or Remote.add() with untrusted URLs containing environment variable expansions. Monitor GitPython releases for updates that disable environment variable expansion in these API calls, similar to the fix applied to Repo.clone_from().