Malicious code in pyyi (PyPI)

The pyyi PyPI package masquerades as a cryptographic library but contains no legitimate cryptographic API. Instead, it installs console scripts named after Python interpreters (e.g., python3.7) that shadow real Python binaries on the system PATH and in common binary locations. When executed, these scripts send the hostname and OS to an obfuscated remote server, then fetch a base64-encoded, gzip-compressed Python payload which is executed in memory via exec without any signature or hash verification. The package also implements a fake Python REPL that disables terminal echo and sends single-token inputs as passwords to the attacker’s server, storing accepted credentials locally in an obfuscated form. The malicious behavior is confirmed by static and isolated dynamic analysis, although the actual server payload and its effects remain unknown. This constitutes installer-side remote code execution and credential theft.

This malicious package enables remote attackers to execute arbitrary Python code on affected systems by supplying payloads from a remote server. It also captures user input in a fake REPL environment to steal credentials. The package shadows legitimate Python interpreters, increasing the likelihood of execution by users or automated systems. The lack of payload integrity verification means attackers can change the executed code at will, potentially leading to full system compromise or data theft.

No official patch or remediation is currently documented. Users should immediately uninstall the pyyi package and remove any shadowed Python interpreter binaries installed by it (e.g., python3.7 in /usr/local/bin, ~/.local/bin, or local app data directories). Avoid installing packages from untrusted sources and verify package authenticity before installation. Monitor for unexpected Python executables on system PATH. Since no vendor advisory or patch information is available, patch status is not yet confirmed — check the vendor advisory or PyPI for updates.