# MAL-2026-5346: Malicious code in cookie-parser-legacy (npm)


- **Type:** Malicious package
- **Package:** `cookie-parser-legacy` (npm)
- **Published:** 9 Jun 2026
- **Also known as:** GHSA-xv3p-wcmf-6hp8

## What is MAL-2026-5346?

MAL-2026-5346 is a malicious package in cookie-parser-legacy, published on 9 Jun 2026. 

### Official description

Package name and README impersonate the well-known `cookie-parser` Express middleware. The source is a near-verbatim copy of cookie-parser, except the legitimate `cookie-signature` dependency has been replaced with an unknown package `moustick` pinned to the mutable `latest` tag (package.json: `"moustick": "latest"`). index.js requires `moustick` as `signature` and invokes `signature.unsign(str.slice(2), secrets[i])` at request time on user-supplied cookie values, executing whatever code `moustick` currently publishes against installer-side cookie secrets and signed values. index.js additionally imports `execSync` from `child_process` at the top of the file with no reference anywhere in the cookie-parsing logic — an unusual staging artifact for a pure parsing module. The combination of name-impersonation of a top-tier middleware, silent substitution of a security-critical dependency, and pinning that substitute to a mutable tag means any installer who picks this up thinking it is `cookie-parser` will resolve and execute arbitrary third-party code controlled by the `moustick` publisher on every install.

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-2026-5346?

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-2026-5346 is a malicious package: cookie-parser-legacy (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-2026-5346/ (Markdown: https://insights.sbomify.com/MAL-2026-5346/index.md)
```

## Sources

- OSV: https://osv.dev/vulnerability/MAL-2026-5346

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From sbomify Insights: https://insights.sbomify.com/MAL-2026-5346/
Summaries are generated and may contain mistakes; the official description above is the record.