Soft Serve is a self-hostable Git server for the command line. From version 0.6.0 to before version 0.11.6, an authorization flaw in repo import allows any authenticated SSH user to clone a server-local Git repository, including another user's private repo, into a new repository they control. This issue has been patched in version 0.11.6.

In Soft Serve, an authenticated repo import can clone server-local private repositories