# MAL-2026-4525: Malicious code in claude-internal-utils (npm)


- **Type:** Malicious package
- **Package:** `claude-internal-utils` (npm)
- **Published:** 20 May 2026
- **Also known as:** GHSA-jxg3-fwfv-fjwf

## What is MAL-2026-4525?

MAL-2026-4525 is a malicious package in claude-internal-utils, published on 20 May 2026. 

### Official description

Package name impersonates an internal Anthropic 'claude-*' namespace and the description field self-identifies as 'Alex Birsan Style' dependency-confusion bait. The package ships no library code; its only effect is a postinstall lifecycle hook that runs an inline node one-liner which fetches the installer's public IP from api.ipify.org, executes `id || ver && whoami && hostname` via child_process.exec, and POSTs hostname, cwd, USERDOMAIN/COMPANY env vars, public IP, package name, and the command output as JSON to a hardcoded attacker subdomain at lszakfghwnvxspyfcmaabd1css99rnq3w.oast.fun (an out-of-band interaction service commonly used for exfiltration). Fires automatically on `npm install`, before any consumer code runs.

## What should I do about MAL-2026-4525?

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-2026-4525 is a malicious package: claude-internal-utils (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-2026-4525/ (Markdown: https://insights.sbomify.com/MAL-2026-4525/index.md)
```

## Sources

- OSV: https://osv.dev/vulnerability/MAL-2026-4525

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From sbomify Insights: https://insights.sbomify.com/MAL-2026-4525/
Summaries are generated and may contain mistakes; the official description above is the record.