# MAL-2026-18357: Malicious code in csvflow-schema (npm)


- **Type:** Malicious package
- **Package:** `csvflow-schema` (npm)
- **Published:** 26 Oct 2026

## What is MAL-2026-18357?

MAL-2026-18357 is a malicious package in csvflow-schema, published on 26 Oct 2026. 

### Official description

csvflow-schema is described as a "Lightweight CSV column-schema validation helper" (index.js exports a small validateSchema function) and adds a postinstall script that runs `node ./postinstall.js` on npm install. postinstall.js writes the username, hostname, working directory, parent process id and install path to `csvflow_schema/pi_2c75177b.ok` in the system temp directory, starts `calc.exe` through `cmd /c start`, and sends an HTTPS GET to `https://cdn-status.mulderitsme.net/pi/2c75177b`, a fixed-id install beacon. The npm account f0x_mulder published 1.0.0 on 2026-10-26, a minute after a 0.0.0-stage placeholder, and npm removed the package 17 minutes later.

csvflow-schema advertises itself as a CSV schema helper but ships a postinstall.js that, on npm install, unconditionally spawns calc.exe via `cmd /c start` and performs an HTTPS GET to the hardcoded non-publisher host cdn-status.mulderitsme.net with a per-install identifier path (/pi/2c75177b). The script also collects local identity data (os.userInfo().username, os.hostname(), process.cwd(), ppid) into a temp file. The code execution primitive (arbitrary child_process spawn at install time) and the callback to a hardcoded third-party host unrelated to any CSV functionality are consistent with a dropper or PoC that proves arbitrary code execution and network reachability on the installer. The declared package purpose (CSV schema helper) has no need for child_process, calculator invocation, or beaconing to an external domain.

## What should I do about MAL-2026-18357?

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-2026-18357 is a malicious package: csvflow-schema (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-2026-18357/ (Markdown: https://insights.sbomify.com/MAL-2026-18357/index.md)
```

## Sources

- OSV: https://osv.dev/vulnerability/MAL-2026-18357

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From sbomify Insights: https://insights.sbomify.com/MAL-2026-18357/
Summaries are generated and may contain mistakes; the official description above is the record.