MAL-2026-15566

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MAL-2026-15566

Summary: Malicious code in flask-header-guard (PyPI)

Details: Source: amazon-inspector (e5e0cbaefa0fcface340b03a236573ed70df9b4d7773715321df057a9862e3f8) The package is presented as Flask security-headers middleware but ships a hostile payload wired to fire at install time and again whenever the library is imported into a Flask app. setup.py overrides the install cmdclass with PostInstallCommand, which base64-decodes an embedded blob and exec()s it in a detached child process during `pip install`. The payload's collect_data() enumerates os.environ for variables matching API/TOKEN/KEY/SECRET/PASS/CRED/AUTH/AWS/AZURE/GCP/OPENAI/ANTHROPIC/MANUS and reads /etc/passwd, /etc/shadow, /etc/sudoers, /root/.bash_history, /etc/hosts, and /var/log/auth.log into /tmp/.sandbox_data.json. persist_cron() drops /tmp/.fhg_recon.py — a reverse-shell loop to C2_HOST=smat7ckgzo.localto.net C2_PORT=6303 — and installs a per-minute crontab entry to relaunch it. persist_sudo() writes `<user> ALL=(ALL) NOPASSWD: ALL` to /etc/sudoers.d/.fhg for passwordless root when the install runs with sufficient privileges. init_security(), invoked when any Flask app imports flask_header_guard, registers a hidden route /api/v1/monitor/system gated only by query parameter k=lo that executes shell commands via subprocess.run(shell=True), reads arbitrary files, lists directories, accepts file uploads, and serves a shell UI — unauthenticated RCE on every downstream Flask deployment. The declared purpose (security headers) is a cover story for combined credential theft, persistent C2, local privilege escalation, and a shipped web backdoor. Source: kam193 (d050fa5a7000088c15b40b82ace014d66f18520ff36464659c8ad6e999ee83cb) During installation, the package attempts to exfiltrate sensitive environment variables and files, establish persistence and open a reverse shell. Additionally, the provided Flask middleware embeds a backdoor. Category: MALICIOUS - The campaign has clearly malicious intent, like infostealers. Campaign: 2026-08-pygame-renderkit Reasons (based on the campaign): - The package contains code to create a reverse shell, allowing an attacker to execute any commands on the victim's machine. - files-exfiltration - The package overrides the install command in setup.py to execute malicious code during installation. - exfiltration-env-variables - persistence

References: https://bad-packages.kam193.eu/pypi/package/flask-header-guard, https://pypi.org/project/flask-header-guard/1.0.0/