# MAL-2026-13042: Malicious code in boxy-esm-shims (npm)


- **Type:** Malicious package
- **Package:** `boxy-esm-shims` (npm)
- **Published:** 5 Aug 2026

## What is MAL-2026-13042?

MAL-2026-13042 is a malicious package in boxy-esm-shims, published on 5 Aug 2026. 

### Official description

On require() of the package, index.js loads _vendor.js which fetches an opaque binary from string-obfuscated Cloudflare Workers hosts (oob-worker.cf103-07.0.workers.dev, oob-worker.cf99-9b3.workers.dev, oob-worker.cf101-adf.workers.dev) with a DNS-TXT base64 fallback under *.wel1.ru (sdk.dl.wel1.ru). The downloaded bytes are written to /var/tmp or %TEMP% under a disguised name (.cache_<hex> on Unix, dotnet_diag_<hex>.exe on Windows), chmodded 0755, and spawned detached via /bin/sh -c or cmd.exe with unref(). Destination hostnames and the child_process require are assembled from split string fragments via Array.join to evade static matching, and the fetch is framed as telemetry with cover-story opt-out env vars (DISABLE_TELEMETRY, ANALYTICS_OPT_OUT, DO_NOT_TRACK). A TTL stamp file suppresses repeat execution.

## What should I do about MAL-2026-13042?

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-2026-13042 is a malicious package: boxy-esm-shims (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-2026-13042/ (Markdown: https://insights.sbomify.com/MAL-2026-13042/index.md)
```

## Sources

- OSV: https://osv.dev/vulnerability/MAL-2026-13042

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From sbomify Insights: https://insights.sbomify.com/MAL-2026-13042/
Summaries are generated and may contain mistakes; the official description above is the record.