# MAL-2026-6309: Malicious code in @nullzero/urlcat (npm)


- **Type:** Malicious package
- **Package:** `@nullzero/urlcat` (npm)
- **Published:** 22 Jun 2026

## What is MAL-2026-6309?

MAL-2026-6309 is a malicious package in @nullzero/urlcat, published on 22 Jun 2026. 

### Official description

@nullzero/urlcat (version 1.4.2, published by nullzero-rlnozk@wshu.net) is a trojanized npm package belonging to the wshu.net credential-stealer campaign. The campaign published trojanized look-alike utility packages across 12+ scopes whose publisher accounts all follow the pattern <scope>-<6 random chars>@wshu.net, with every scope created on June 4, 2026 in a ~40-minute burst. Like the other packages in the campaign, it declares a postinstall hook ("node lib/encoder.js") that runs a bundled payload file automatically on npm install. The campaign payload is a Chromium browser credential stealer that reads Chromium Cookies and Login Data, decrypts saved passwords protected by AES-256-GCM (the v10/v11 app-bound key schemes), and exfiltrates them over HTTPS using a spoofed Mozilla/5.0 user agent, hidden behind javascript-obfuscator obfuscation (hex identifiers, a while (!![]) array-rotation IIFE, base64+RC4 string decoding, control-flow flattening, and runtime-decrypted module resolution). This package was unpublished from npm before the payload could be captured, so its specific payload was not independently verified; it is reported on the basis of its membership in the wshu.net campaign (matching publisher email pattern, scope-creation burst, and postinstall execution pattern).

Package `@nullzero/urlcat` impersonates the legitimate `urlcat` URL-builder library — same advertised `cat(base, path, params)` API, README copied from upstream, and `package.json.repository.url` points to `git+https://github.com/balazsbotond/urlcat.git` (the real upstream maintainer's repo, not the `nullzero` publisher's). The package main `lib/index.js` line 64 calls `encoder.runPrepare()` at the top of every invocation of the exported `cat()` function. `lib/encoder.js` is a 263 KB obfuscator.io-packed file (rotated 1176-entry string array, RC4 decoder `_0x2f0d`, control-flow flattening) — far beyond anything a tiny URL composer requires. Decoded control flow in `lib/encoder.js` selects a platform-specific binary candidate (branches on `process.platform === 'win32'` to `'win.js'` / a bun-style executable, otherwise a node-typed binary), constructs a destination under `os.tmpdir()`, downloads it over `https.request` following up to 5 redirects with `User-Agent: node-installer`, sha256-checks against a `.meta` JSON sidecar, and then `spawn`s the dropped binary (or re-execs `process.execPath` against it) detached + unref'd, with a private env-var marker (`__7D0A53...`). The encoder also installs no-op handlers for `uncaughtException`, `unhandledRejection`, and `SIGINT` to suppress crashes, performs obfuscator.io-style debugger-detection (`Function('debugger')` regex self-check), and re-spawns the current node when run interactively so the payload runs only in the detached child. A URL-builder library has no legitimate need for a 263 KB obfuscated sibling, a platform-specific binary download, anti-debug guards, or a detached child re-exec. Any consumer who calls `cat()` triggers arbitrary code execution from an attacker-controlled binary on their machine.

## What should I do about MAL-2026-6309?

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-2026-6309 is a malicious package: @nullzero/urlcat (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-2026-6309/ (Markdown: https://insights.sbomify.com/MAL-2026-6309/index.md)
```

## Sources

- OSV: https://osv.dev/vulnerability/MAL-2026-6309

---
From sbomify Insights: https://insights.sbomify.com/MAL-2026-6309/
Summaries are generated and may contain mistakes; the official description above is the record.