Launch Week Day 1: Announcing Security Design Review
CRITICAL PyPI Malware

Malicious code in uprobe (PyPI)

MAL-2026-5279

Published ยท Modified

Description


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Source: amazon-inspector (82230ac4ef4464e9696491bf25cfabbd5cff78ab2256f4aa1a0d5ad7456218a8)

The package installs uprobe-setup.pth, which Python auto-loads at every interpreter startup in any environment where the wheel is present. The.pth contents alias stdlib modules to single-underscore short names (_O, _T, _o, _s, _u, _p, _y, _g, _zf) and wrap the payload in exec('...') gated by a /tmp/.bun_ran sentinel. The payload globs for a sibling _index.js under the package directory, downloads the Bun JavaScript runtime ZIP from https://github.com/oven-sh/bun/releases/download/bun-v1.3.13/bun-{platform}-{arch}.zip to /tmp/b/bun, chmods it 0o775, and invokes subprocess.run([bun, 'run', _index.js]). This is an alternate-runtime dropper: a foreign runtime is fetched and used to execute bundled JavaScript that is opaque to any Python-side review. The behavior fires unconditionally on python startup (not just on explicit tool invocation), runs outside pip's build isolation, and the obfuscation + exec-on-string + sentinel-gated one-shot pattern is canonical evasion shape. The advertised purpose of the package (a FISH-probe design tool) has no need for a JavaScript runtime.

Source: kam193 (d6d0df66bf8ff6eaf447d14185b7df7a06bafc9cea9de3611a2dcc594cf97ec3)

Versions 0.1.3, 0.1.4 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

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