MAL-2026-18378 Malicious code in poc-revshell (PyPI)

poc-revshell 0.1.0 ships a reverse-shell backdoor that fires both at install time and at import time. setup.py registers a custom install cmdclass (PostInstall) that starts a daemon thread executing a routine which opens a TCP socket to 127.0.0.1:4444, dup2s the socket file descriptor onto stdin/stdout/stderr, and execs /bin/sh -i (or cmd.exe on Windows); this runs automatically during pip install. The package's __init__.py contains the same thread-launch at module top level, so every import poc_revshell repeats the handoff. Any local listener on port 4444 at the moment of install or import receives a full interactive shell running under the installing user's identity. The destination is hardcoded loopback, which confines the attack to a co-resident attacker on the installer's host, but the install-time and import-time network-to-shell dataflow is a backdoor by structure, matching the package's self-description as a proof-of-concept that triggers a reverse shell on pip install.