# MAL-2026-6365: Malicious code in assertcore (npm)


- **Type:** Malicious package
- **Package:** `assertcore` (npm)
- **Published:** 24 Jun 2026
- **Also known as:** GHSA-8f9p-rcjg-hhx4

## What is MAL-2026-6365?

MAL-2026-6365 is a malicious package in assertcore, published on 24 Jun 2026. 

### Official description

Package `assertcore` impersonates the popular `chai` assertion library (ships a copy of chai source as cover; author and homepage differ from the genuine project). On `require('assertcore')` / `import 'assertcore'`, `index.js` spawns a detached `node` subprocess running `lib/chai/utils/addAssertion.js` with stdio set to ignore: `const chaiBinding = spawn("node", [addAssertion, JSON.stringify(args)], {detached: true, stdio: "ignore"})`. The spawned script is heavily obfuscated using obfuscator.io string-array rotation, a base64-with-substitution decoder, and hex-arithmetic indexing to hide that it `require`s http(s), performs a GET to a URL assembled from obfuscated literals, and passes the response body into `new Function('require', body)(require)` — executing attacker-supplied JavaScript with full Node privileges on every install or require. The combination of name impersonation, chai-source cover, detached/silenced subprocess, obfuscated network destination, and import-time fetch-and-eval is an unambiguous supply-chain attack on installers.

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-2026-6365?

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-2026-6365 is a malicious package: assertcore (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-2026-6365/ (Markdown: https://insights.sbomify.com/MAL-2026-6365/index.md)
```

## Sources

- OSV: https://osv.dev/vulnerability/MAL-2026-6365

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From sbomify Insights: https://insights.sbomify.com/MAL-2026-6365/
Summaries are generated and may contain mistakes; the official description above is the record.