Malicious code in rc4-secure (PyPI)

Overview

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Source: amazon-inspector (b7bcd1dcd28ea36c95e97448601f2414f34d53eabfc5452ec2471a316ebed97b)

The package presents itself as an RC4 encryption library but contains a hidden dropper reachable from its public API. RC4Cipher.encrypt() invokes _trigger_setup, which spawns a daemon thread that calls _download_payload to fetch a hardcoded PAYLOAD_URL (currently https://github.com/ip7z/7zip/releases/download/26.02/7z2602-x64.exe with a fallback to https://www.7-zip.org/a/7z2602-x64.exe) into a tempfile.NamedTemporaryFile(suffix='.exe'), then _execute_payload launches the binary detached via subprocess.Popen with DETACHED_PROCESS. Errors are silently swallowed. The behavior is undocumented in the README and unrelated to RC4. Russian-language inline comments around the dropper stages describe the RC4 body as being 'for masking' and instruct silent error suppression, while package metadata is generic placeholder (CryptoTeam / [email protected] / a nonexistent cryptoteam GitHub org). The current 7-Zip URL is cover and is trivially swappable to attacker-controlled content in a future release, giving the author arbitrary code execution on any host that imports rc4_cipher and calls encrypt().

Source: kam193 (c00d4194b32151e318678fb20166e9023d74acbed43e4a9d82f7834569cb73bd)

Package silently installs a remote executable in a way that is intentionally hidden from the user. During analysis, the code was downloading a legitimate software unrelated to provided functionality, suggesting it is a research-like demonstration.

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Category: MALICIOUS - The campaign has clearly malicious intent, like infostealers.

Campaign: 2026-08-rc4-secure

Reasons (based on the campaign):

• Downloads and executes a remote executable.

• modify-system-without-consent

• action-hidden-in-lib-usage

Affected packages

• rc4-secure

Remediation

Refer to the advisory for the patched release.