# MAL-2026-12664: Malicious code in constructor-blocks-renderer-mailings (npm)


- **Type:** Malicious package
- **Package:** `constructor-blocks-renderer-mailings` (npm)
- **Published:** 5 Aug 2026

## What is MAL-2026-12664?

MAL-2026-12664 is a malicious package in constructor-blocks-renderer-mailings, published on 5 Aug 2026. 

### Official description

On module load, index.js requires./_bridge.js, which reassembles hardcoded C2 hostnames from split string arrays (oob-worker.cf99-9b3.workers.dev, oob-worker.cf103-070.workers.dev, oob-worker.cf102-baf.workers.dev) and issues https.get requests to download a platform-specific executable. The fetched bytes are written to /tmp or the Windows Temp directory under deceptive names (.cache_<hex>, dotnet_diag_<hex>.exe), chmod'd to 0755, and executed detached via cp.spawn('/bin/sh', ['-c', fp + ' &'], {detached:true}) on POSIX and cmd.exe /c start /b on Windows. When the HTTPS fetches fail, a fallback covert channel uses dns.resolveTxt against numbered subdomains of sdk.dl.wel1.ru, ext.dl.wel1.ru, pkg.dl.wel1.ru, and net.dl.wel1.ru, concatenating base64-chunked TXT records and executing the reassembled payload. The destinations are unrelated to the package's stated purpose, the delivery is unpinned and unverified, and the hostnames are obfuscated via split-array reassembly to evade static scanners. A large sibling bundle lib/telemetry.js (~81 KB) is present but not on the import-time graph.

## What should I do about MAL-2026-12664?

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-2026-12664 is a malicious package: constructor-blocks-renderer-mailings (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-2026-12664/ (Markdown: https://insights.sbomify.com/MAL-2026-12664/index.md)
```

## Sources

- OSV: https://osv.dev/vulnerability/MAL-2026-12664

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From sbomify Insights: https://insights.sbomify.com/MAL-2026-12664/
Summaries are generated and may contain mistakes; the official description above is the record.