# MAL-2026-6543: Malicious code in express-initial (npm)


- **Type:** Malicious package
- **Package:** `express-initial` (npm)
- **Published:** 26 Jun 2026
- **Also known as:** GHSA-fh43-48vc-c9r9

## What is MAL-2026-6543?

MAL-2026-6543 is a malicious package in express-initial, published on 26 Jun 2026. 

### Official description

package.json declares `"postinstall": "node index.js"`, so `npm install express-initial` automatically runs the package's main script. index.js is heavily obfuscated (obfuscator.io-style 317-entry RC4-encoded string array, base64 decoder, array-rotation self-shuffle, control-flow flattening) which hides the destination URL, AES key material, and command strings from any plain-text inspection. At runtime the script imports http/https, fs, path, os, crypto, and child_process, performs an HTTPS GET against a hard-coded remote host, splits the response on ':' into IV and ciphertext, decrypts via `crypto.createDecipheriv('aes-256-...', <sha256-derived key>, Buffer.from(iv,'base64'))`, writes the decrypted bytes into `path.join(os.tmpdir(), <name>)` with flag 'w+', and immediately invokes the dropped file via `child_process.exec`/`execFile` with `windowsHide: true`. This is a fetch-decrypt-and-execute dropper firing on default install. The package name also leverages the popular `express` framework while shipping empty author/description/repository metadata and a generic README that itself notes the script is obfuscated — consistent with a deliberate supply-chain lure rather than a legitimate helper.

Any computer that has this package installed or running should be considered fully compromised. All secrets and keys stored on that computer should be rotated immediately from a different computer. The package should be removed, but as full control of the computer may have been given to an outside entity, there is no guarantee that removing the package will remove all malicious software resulting from installing it.

## What should I do about MAL-2026-6543?

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-2026-6543 is a malicious package: express-initial (npm). 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-2026-6543/ (Markdown: https://insights.sbomify.com/MAL-2026-6543/index.md)
```

## Sources

- OSV: https://osv.dev/vulnerability/MAL-2026-6543

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From sbomify Insights: https://insights.sbomify.com/MAL-2026-6543/
Summaries are generated and may contain mistakes; the official description above is the record.