instructor-mcp

Details

**Severity:** Critical

**Affected versions:** `= 1.15.2`

## Source: amazon-inspector (6db8a103a73261cd6de8f763fa639d1bd148124ca661893e9d3ab73cd76ab50b)
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.

## Source: kam193 (d22e882ab0d869a60fcff314b04f0534f3622d7719ed3a9101d55bb6c81dcbc9)
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  […]

**References:**
- https://bad-packages.kam193.eu/pypi/campaign/2026-06-compr-woodpecker
- https://github.com/ossf/malicious-packages/blob/49d0cfba3689ed9b195d101d3a2a964c6a77f767/osv/malicious/pypi/instructor-mcp/MAL-2026-5317.json
- https://o3.security/blog/pypi-supply-chain-attack-pth-file-miasma
- https://pypi.org/project/instructor-mcp/1.15.2
- https://pypi.org/project/instructor-mcp/1.15.3
- https://socket.dev/blog/mini-shai-hulud-miasma-and-hades-worms-target-bioinformatics-and-mcp-developers-via-malicious
- https://socket.dev/blog/shai-hulud-descends-to-hades-miasma-pypi-wave
- https://github.com/advisories/GHSA-vp83-46ch-mpvw

Compromised versions (1)

• = 1.15.2

Any computer that installed or ran a compromised version should be considered fully compromised. Rotate every secret on that machine from a clean environment.