# MAL-2026-5317: Malicious code in instructor-mcp (PyPI)


- **Type:** Malicious package
- **Package:** `instructor-mcp` (PyPI)
- **Published:** 6 Jun 2026
- **Also known as:** PYSEC-2026-1069

## What is MAL-2026-5317?

MAL-2026-5317 is a malicious package in instructor-mcp, published on 6 Jun 2026. 

### Official description

instructor-mcp 1.15.2 is a typosquat of the legitimate `instructor` PyPI library (it copies the same author names, README, and repository URL `github.com/instructor-ai/instructor`) and ships an additional file `instructor-setup.pth` that the Python interpreter auto-executes on every `python` invocation after install. The.pth file uses an obfuscated single-line `exec(...)` with mangled aliases (`_o,_s,_u,_p,_y,_h,_g`) to bypass the `.pth` rule that only `import` lines execute. The exec body downloads the Bun JavaScript runtime from `https://github.com/oven-sh/bun/releases/download/bun-v1.3.13/bun-{platform}-{arch}.zip` to `/tmp/b/bun`, chmods it executable, then searches `sys.path` for a file named `_index.js` and runs it via `bun run _index.js`. Execution is gated by `/tmp/.bun_ran` so it fires once per host. There is no hash/signature check on the downloaded runtime, and the JS payload is whatever `_index.js` happens to be present on `sys.path` (shipped by a co-installed package or planted by a separate component) — bypassing Python static analysis entirely. This is the alternate-runtime-dropper pattern: arbitrary attacker-controlled JS is executed under a freshly downloaded non-Python runtime, with persistence via the.pth auto-load mechanism.

Versions 1.15.2, 1.15.3 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-2026-5317?

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-2026-5317 is a malicious package: instructor-mcp (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-2026-5317/ (Markdown: https://insights.sbomify.com/MAL-2026-5317/index.md)
```

## Sources

- OSV: https://osv.dev/vulnerability/MAL-2026-5317

---
From sbomify Insights: https://insights.sbomify.com/MAL-2026-5317/
Summaries are generated and may contain mistakes; the official description above is the record.