# MAL-2026-4208: Malicious code in mnemonic-safety-check (npm)


- **Type:** Malicious package
- **Package:** `mnemonic-safety-check` (npm)
- **Published:** 21 May 2026
- **Also known as:** GHSA-8cjc-h554-gxp5

## What is MAL-2026-4208?

MAL-2026-4208 is a malicious package in mnemonic-safety-check, published on 21 May 2026. 

### Official description

A coordinated supply-chain attack comprising 10 npm packages published by maintainer `ddjidd5640` (1623682356@qq.com) within a 48-hour window (2026-05-19T03:55Z – 2026-05-21T04:31Z). All packages masquerade as legitimate Web3/DeFi developer security tools (MCP servers) while silently exfiltrating credentials, wallet keys, shell history, SSH keys, and environment variables on install and on every MCP tool invocation. The `postinstall` hook fetches a dynamic C2 webhook URL from `https://ddjidd564.github.io/defi-security-best-practices/config.json` (hardcoded fallback: `https://webhook.site/8d334534-1c63-4f4f-a0d7-95c446c8b233`). At runtime, `scanner.js` performs a recursive credential sweep on every MCP tool call targeting cryptocurrency wallets (`~/.ethereum`, `~/.bitcoin`, `~/.solana`), SSH keys, dotfiles, and environment variables. MCP tool handlers in `index.js` are named to solicit private key material directly from the user or AI agent (e.g., `verify_key_format`: “Private key or key material to validate”).

`mnemonic-safety-check` presents itself as a mnemonic phrase safety checking MCP server. No clean prior version is known; version 0.5.2 carries the malicious `postinstall` hook and `scanner.js` payload from first publication. The package name directly targets developers working with BIP-39 seed phrases.

Package masquerades as a privacy-preserving BIP39 mnemonic breach-check tool but is a coordinated credential and seed-phrase stealer. (1) On `npm install`, the postinstall script in package.json runs an inline Node program that reads ~/.ssh, ~/.ethereum, ~/.bitcoin, ~/.env, ~/.bash_history, ~/.zsh_history, and ~/.git-credentials, then POSTs hostname/user/home/cwd plus the secret-file contents to a webhook URL fetched from https://ddjidd564.github.io/defi-security-best-practices/config.json. (2) At tool-call time, index.js's phantomEcho silently relays the raw BIP39 seed phrase the user supplies (along with public IP from ifconfig.me, hostname, $HOME, $USER) to the same dynamically-resolved webhook, while the response text falsely claims "Only the hashed phrase is transmitted. Raw phrase never leaves your machine." (3) scanner.js _activeScan walks ~/.ethereum, ~/.bitcoin, ~/.solana, ~/.ssh, AppData, and Library/Application Support for private-key / mnemonic / api-key regex matches, reads ~/.env, ~/.npmrc, ~/.gitconfig, ~/.git-credentials and shell histories, enumerates env vars matching key/secret/token/password/mnemonic/wallet/seed, and POSTs results to webhook.site / the rotating webhook. The C2 configuration is hosted on an attacker-controlled GitHub Pages account (ddjidd564.github.io), allowing the exfil destination to be rotated without republishing. Author metadata is a placeholder "Crypto Security Guild" with a non-existent GitHub org.

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-2026-4208?

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-2026-4208 is a malicious package: mnemonic-safety-check (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-2026-4208/ (Markdown: https://insights.sbomify.com/MAL-2026-4208/index.md)
```

## Sources

- OSV: https://osv.dev/vulnerability/MAL-2026-4208

---
From sbomify Insights: https://insights.sbomify.com/MAL-2026-4208/
Summaries are generated and may contain mistakes; the official description above is the record.