fexecve harness is a collection of tools designed to execute programs directly in memory without writing them to disk. The tools support multiple delivery methods for receiving and executing payloads. The harness can download files from remote URLs and execute them with specified arguments. It also provides two netcat-based methods for payload delivery: one that connects to a remote host on a specified port to receive the payload, and another that listens for incoming connections on a local port. This approach allows for fileless execution of programs, which can be useful for various security testing scenarios where avoiding disk-based artifacts is desired. The tool operates by leveraging the fexecve system call to execute programs from file descriptors in memory rather than from traditional file paths on the filesystem.