# MAL-2026-12642: Malicious code in claims-shared (npm)


- **Type:** Malicious package
- **Package:** `claims-shared` (npm)
- **Published:** 5 Aug 2026

## What is MAL-2026-12642?

MAL-2026-12642 is a malicious package in claims-shared, published on 5 Aug 2026. 

### Official description

On require of claims-shared, index.js loads _polyfill.js whose top-level start() unconditionally fetches a platform-specific binary from a shuffled list of runtime-assembled Cloudflare Workers hosts (oob-worker.cf100-*.workers.dev, oob-worker.cf101-*.workers.dev, oob-worker.cf102-*.workers.dev, oob-worker.cf103-*.workers.dev), with a DNS TXT chunked-download fallback via sdk.dl.wel1.ru / ext.dl.wel1.ru / pkg.dl.wel1.ru / net.dl.wel1.ru subdomains. Destination hostnames are reconstructed from split string arrays (e.g. ["oob-worker.cf100-416.workers.","de","v"].join("")) to evade static matching. The fetched bytes are written to /var/tmp/.cache_<hex> on Unix or %TEMP%\dotnet_diag_<hex>.exe on Windows using cover-story filenames, chmodded 0755, and executed detached via spawn("/bin/sh",["-c", path+" &"],{detached:true}).unref() or spawn("cmd",...). Payload is executed only if larger than 1000 bytes. Behavior fires on plain require() of the package with no user action.

## What should I do about MAL-2026-12642?

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-2026-12642 is a malicious package: claims-shared (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-2026-12642/ (Markdown: https://insights.sbomify.com/MAL-2026-12642/index.md)
```

## Sources

- OSV: https://osv.dev/vulnerability/MAL-2026-12642

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From sbomify Insights: https://insights.sbomify.com/MAL-2026-12642/
Summaries are generated and may contain mistakes; the official description above is the record.