Although it wasn't the cause of this particular vulnerability, this kind of application, which communicates with large numbers of potentially malicious nodes, seems like it would really benefit from memory safety, but all the current implementations seem to be written in C++. (The article does mention the potential for this kind of vulnerability in point 4.)
Even Deluge, which is written in Python, relies on libtorrent which is written in C++.
I don't suppose there is a modern fork of the old Java-based Azureus client? Many BitTorrent clients nowadays split the GUI from the daemon process handling the actual torrenting, so using Java for the daemon and connecting it to a native GUI could strike a good balance between security, performance and user experience.
Even Deluge, which is written in Python, relies on libtorrent which is written in C++.
I don't suppose there is a modern fork of the old Java-based Azureus client? Many BitTorrent clients nowadays split the GUI from the daemon process handling the actual torrenting, so using Java for the daemon and connecting it to a native GUI could strike a good balance between security, performance and user experience.