MalwarePublished 6 Jun 2026Updated 9 Jul 2026

mrbios (PyPI) · Malicious Code

Affects mrbiosSource GCVE Database

Malicious package : remove mrbios and rotate any secrets on hosts that installed it.

Data as of 11 Jul 2026, 09:43 UTC

Classification

Malicious package

Published to PyPI · OSV MAL-2026-5282

What to do

Remove mrbios from every project, lockfile and image that pulls it in. Treat any host that installed it as compromised: rotate the credentials, tokens and keys it could read, from a clean machine.

Affected software

Product	Affected	Fixed in
PyPImrbios	Affected =0.1.1 =0.1.2	Fixed in–

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Description

--- _-= Per source details. Do not edit below this line.=-_ ## Source: amazon-inspector (8d1c97dced5d8f917e2e9901e0ed99fb0034bfafb5a3d46ad47eeba76a883c57) The package installs `mrbios-setup.pth` into site-packages. Python auto-loads.pth files at every interpreter startup, so the contained payload runs unconditionally for any `python` invocation on a machine where mrbios has been installed — not just when the package is explicitly imported. The payload is wrapped in an `exec()` of a string built from single-letter aliased imports (`_o`, `_s`, `_u`, `_p`, `_y`, `_T`, `_G`) to evade static review. When executed, it downloads the Bun JavaScript runtime from `https://github.com/oven-sh/bun/releases/download/bun-v1.3.13/bun-{os}-{arch}.zip` to `/tmp/b/bun`, chmods it executable (mode 509 / 0o775), and invokes it to run a sibling `_index.js` shipped in the package. A `/tmp/.bun_ran` sentinel gates re-execution per temp directory. The package advertises itself as a 'bioinformatics scripts management tool' and has no documented need for a JavaScript runtime; the JS payload runs outside Python's introspectable surface, so its behavior is not visible to ordinary Python tooling. The combination of unconditional auto-execution via.pth, deliberate obfuscation, alien-runtime fetch from a non-publisher source, and execution of bundled JavaScript whose contents are opaque to the Python ecosystem constitutes an install/startup-time remote code execution surface against any installer. ## Source: kam193 (3bc0ad232af6f3dafcf2d02441531485e0b459c2659542375c62f4f7003c9e08) Versions 0.1.1, 0.1.2 were compromised. Compromised packages start an obfuscated infostealer. The infostealer is a heavily obfuscated JavaScript code executed using Bun runtime on Python startup. It collectes all kinds of sensitive data, including API keys, credentials to package repositories, cryptocurrency assets, password manager data. Infostealer actively queries online services to collect additional secrets as well as attempts to gain persistence and spread further by publishing infected packages using collected credentials. Data are exfiltrated likely using Github. The code seems to threaten to wipe the user's data if it detects invalid GitHub tokens. Cleanup should be done with caution. It seems to be related to the recent Mini Shai Hulud campaign. --- Category: MALICIOUS - The campaign has clearly malicious intent, like infostealers. Campaign: 2026-06-compr-woodpecker Reasons (based on the campaign): - compromised-package - exfiltration-env-variables - exfiltration-cloud-tokens - exfiltration-credentials - abuses-pth - obfuscation - infostealer - The package contains code to detect if it is running in a sandbox environment. - exfiltration-crypto - files-exfiltration - destructive-actions

Impact

Any system with mrbios versions 0.1.1 or 0.1.2 installed is subject to remote code execution on every Python interpreter startup. The malicious payload can exfiltrate sensitive data including API keys, credentials, cryptocurrency assets, and password manager information. It can also spread by publishing infected packages using stolen credentials and may destroy user data under certain conditions. The threat compromises confidentiality, integrity, and availability of affected systems and data.

Defensive guidance

Users should immediately uninstall the mrbios package versions 0.1.1 and 0.1.2 and remove any installed .pth files related to mrbios to prevent automatic execution. Due to the destructive potential of the malware, cleanup should be performed with caution, ideally on isolated systems. Monitor for any unauthorized package publishing activity using your credentials. Check vendor advisories or PyPI security notices for updates or official remediation guidance.

Summary

The mrbios package installs a .pth file that causes Python to execute obfuscated code on every interpreter start, regardless of explicit import. This code downloads the Bun JavaScript runtime from a third-party GitHub release and runs a bundled obfuscated JavaScript infostealer. The infostealer collects a wide range of sensitive information including environment variables, cloud tokens, package repository credentials, cryptocurrency assets, and password manager data. It also queries online services for additional secrets, attempts to maintain persistence, and spreads by publishing infected packages using stolen credentials. The code includes sandbox detection and may perform destructive actions such as wiping user data if invalid GitHub tokens are found. Versions 0.1.1 and 0.1.2 of mrbios are compromised. The package falsely advertises itself as a bioinformatics tool, and the malicious payload operates outside normal Python introspection, evading detection by standard Python security tools. This constitutes a severe remote code execution and data exfiltration threat.

References

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What to do

Affected software

Description

AI analysisMachine-generated, updated 10 Jul 2026, 09:36 UTC

Technical details

References

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