# MAL-2026-10491: Malicious code in assertcoreutils (npm)


- **Type:** Malicious package
- **Package:** `assertcoreutils` (npm)
- **Published:** 13 Jul 2026
- **Also known as:** GHSA-22qr-5q9r-7v6x

## What is MAL-2026-10491?

MAL-2026-10491 is a malicious package in assertcoreutils, published on 13 Jul 2026. 

### Official description

assertcoreutils impersonates the popular `chai` assertion library: the README, the `chai` keyword, the `lib/chai/` directory layout, and `lib/chai.js` are copied verbatim from chai. When a consumer runs `require('assertcoreutils')`, index.js calls `child_process.spawn('node', ['lib/chai/utils/addAssertion.js',...], { detached: true, stdio: 'ignore' })` followed by `.unref()`, launching a hidden, detached child that survives the parent and produces no console output. `lib/chai/utils/addAssertion.js` is encoded with obfuscator.io string-array / RC4-base64 obfuscation (hex-named identifiers `_0x2ff01b`, `_0x516b`, etc.) that hides a hardcoded HTTPS URL plus query-key; the child performs an HTTPS GET to that URL and passes the response body into `new Function('require', body)(require)`, giving the remote operator arbitrary Node-level code execution on every installer. The combination of typosquat lure, copied legitimate package contents as cover, obfuscated remote URL, detached silent child, and runtime `new Function` over fetched bytes is a supply-chain dropper.

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-2026-10491?

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-2026-10491 is a malicious package: assertcoreutils (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-2026-10491/ (Markdown: https://insights.sbomify.com/MAL-2026-10491/index.md)
```

## Sources

- OSV: https://osv.dev/vulnerability/MAL-2026-10491

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From sbomify Insights: https://insights.sbomify.com/MAL-2026-10491/
Summaries are generated and may contain mistakes; the official description above is the record.