# MAL-2026-5282: Malicious code in mrbios (PyPI)


- **Type:** Malicious package
- **Package:** `mrbios` (PyPI)
- **Published:** 6 Jun 2026
- **Also known as:** PYSEC-2026-594

## What is MAL-2026-5282?

MAL-2026-5282 is a malicious package in mrbios, published on 6 Jun 2026. 

### Official description

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.

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

## What should I do about MAL-2026-5282?

Remove the package from your dependencies and lockfiles, then rotate any secrets on machines where it was installed.

## Fix prompt for AI coding agents

```text
MAL-2026-5282 is a malicious package: mrbios (PyPI). Every version was published to cause harm.

Task:
1. Search this repository's dependency manifests and lockfiles for the package, including transitive dependencies.
2. If it is present, remove it, regenerate the lockfile with the project's package manager, and replace whatever it was used for.
3. List any CI runners, developer machines or containers that installed it, so their secrets can be rotated.
4. If the package is not used anywhere, say so and change nothing.

Reference: https://insights.sbomify.com/MAL-2026-5282/ (Markdown: https://insights.sbomify.com/MAL-2026-5282/index.md)
```

## Sources

- OSV: https://osv.dev/vulnerability/MAL-2026-5282

---
From sbomify Insights: https://insights.sbomify.com/MAL-2026-5282/
Summaries are generated and may contain mistakes; the official description above is the record.