# MAL-2026-6437: Malicious code in logfmt-core (npm)


- **Type:** Malicious package
- **Package:** `logfmt-core` (npm)
- **Published:** 25 Jun 2026
- **Also known as:** GHSA-q37m-wc54-rhg8

## What is MAL-2026-6437?

MAL-2026-6437 is a malicious package in logfmt-core, published on 25 Jun 2026. 

### Official description

On npm install, scripts/install-check.cjs (registered as a postinstall lifecycle script) fetches a JSON config from a hardcoded anonymous Vercel app URL (https://vercel-backend-myapp.vercel.app/config/logfmt-sync.json), parses it to obtain a.tgz bundle URL, downloads the tarball to /tmp, extracts it with tar -xzf, runs `npm install` inside the extracted directory (causing any lifecycle scripts in the fetched package to also run), then require()s peer-math.js from the bundle and invokes syncSession(). The fetched code is unpinned, unauthenticated, not hash-verified, not hosted on the publisher's domain, and unrelated to the package's stated purpose (a logging-format utility offering createLogger, formatCurrency, roundDecimal). The package author controls the Vercel endpoint and can change the delivered bytes at any time, giving them arbitrary code execution on every machine that installs logfmt-core. Naming choices (`install-check`, `resolvePeerBundleUrl`, `runPeerSync`, `syncSession`) and a benign-looking `[logfmt-core] install check skipped` error log are framed to resemble a routine peer-dependency check rather than a remote-payload loader.

Any computer that has this package installed or running should be considered fully compromised. All secrets and keys stored on that computer should be rotated immediately from a different computer. The package should be removed, but as full control of the computer may have been given to an outside entity, there is no guarantee that removing the package will remove all malicious software resulting from installing it.

## What should I do about MAL-2026-6437?

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-2026-6437 is a malicious package: logfmt-core (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-2026-6437/ (Markdown: https://insights.sbomify.com/MAL-2026-6437/index.md)
```

## Sources

- OSV: https://osv.dev/vulnerability/MAL-2026-6437

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From sbomify Insights: https://insights.sbomify.com/MAL-2026-6437/
Summaries are generated and may contain mistakes; the official description above is the record.