AsyncSSH: SFTP Recursive Copy Path Traversal via Unsanitized Server-Supplied Filenames

AsyncSSH is a Python package which provides an asynchronous client and server implementation of the SSHv2 protocol on top of the Python asyncio framework. Prior to 2.24.1, recursive remote-to-local SFTP copies in SFTPClient._copy() in asyncssh/sftp.py, reached through get(), mget(), and copy(), trust filenames returned by a remote server's directory enumeration. A malicious or compromised SFTP server can return an absolute filename or a filename containing path separators and parent-directory traversal, causing destination path construction to escape the requested local directory and write attacker-selected content to locations writable by the client process. This issue is fixed in version 2.24.1.