---
id: "MAL-2026-18357"
kind: "package"
aliases: ["MAL-2026-18357"]
title: "Malicious code in csvflow-schema (npm)"
severity: "critical"
cvss: null
epss: null
exploited: false
status: "open"
category: "package"
products: [{"name": "csvflow-schema", "fixed": [], "affected": "= 1.0.0", "ecosystem": "npm"}]
ecosystems: ["npm"]
tags: ["malicious", "package"]
not_affected_if: []
published_at: "2026-10-26T18:22:11+00:00"
first_seen_at: "2026-10-28T07:01:41+00:00"
updated_at: "2026-10-28T07:07:01+00:00"
sources: [{"source": "osv-malicious", "url": "https://osv.dev/vulnerability/MAL-2026-18357", "first_seen_at": "2026-10-28T07:01:41+00:00"}]
---

# Malicious code in csvflow-schema (npm)

## Affected

- npm:csvflow-schema affected = 1.0.0 fixed ?

## Timeline

- 2026-10-28T07:01:41+00:00 osv-malicious https://osv.dev/vulnerability/MAL-2026-18357

## From the sources

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.

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