rssh version 2.3.4 contains a CWE-77: Improper Neutralization of Special Elements used in a Command ('Command Injection') vulnerability in allowscp permission that can result in Local command execution. This attack appear to be exploitable via An authorized SSH user with the allowscp permission.
Insufficient sanitization of arguments passed to rsync can bypass the restrictions imposed by rssh, a restricted shell that should restrict users to perform only rsync operations, resulting in the execution of arbitrary shell commands.