Installation

Installation

Three ways to run the server. Docker is the recommended one — it pins Node, the operating system and every dependency, which matters here because CyberChef's operation set reaches into native crypto and image libraries.

Docker

docker run -i --rm ghcr.io/doublegate/cyberchef-mcp_v3:latest

Tag	Points at
latest	The newest release
3.0.0	An exact version — use this in anything you depend on
3.0	The newest patch of 3.0
3	The newest 3.x

The package name carries the major, so the v2.x line stays reachable at ghcr.io/doublegate/cyberchef-mcp_v2 with its own 2.10.0 / 2.10 / 2 / latest tags, and v1.9.x at _v1. A major release renames the image rather than superseding the old one.

Also published to Docker Hub as parobek/cyberchef-mcp. Both registries carry the same image, built once and pushed to both, with provenance and SBOM attestations.

-i is mandatory. stdio transport means the server reads JSON-RPC from standard input; without -i Docker gives it no stdin and the process exits immediately.

--rm is a convenience, not a requirement — it cleans up the container when the client disconnects. Without it you accumulate stopped containers.

The image runs as UID 65532 (nonroot) on a Chainguard Wolfi base.

It is not shell-free. This page said "contains no shell" until v3.2.0, and measuring the published image found /usr/bin/sh, ash, busybox (v1.38.0) and npm. What is genuinely absent is a package manager: no apk, no wget, no curl. If your threat model assumed no shell, it needs revisiting — see the v3.1.0 baseline.

npm

npx cyberchef-mcp

Published as cyberchef-mcp since 2.5.0. Requires Node >=24 <27, matching upstream CyberChef's own floor, and carries a second binary — cyberchef-migrate, the v1-to-v2 migration helper.

This section said "prepared, not yet published" until v3.0.0. Publishing was prepared in v2.3.0; the first release that actually published was v2.5.0, and no document was updated when it succeeded. Corrected against npm view cyberchef-mcp versions.

Docker is still the recommended route — it pins Node, the operating system and every dependency, which matters because CyberChef's operation set reaches into native crypto and image libraries.

From source

git clone https://github.com/doublegate/CyberChef-MCP.git
cd CyberChef-MCP
npm install
npx grunt configTests    # REQUIRED -- generates two files that are not committed
npm run mcp

npx grunt configTests is not optional. It generates src/core/config/OperationConfig.json and src/node/index.mjs, both of which are gitignored because they are build products. Skipping it produces:

Error [ERR_MODULE_NOT_FOUND]: Cannot find module './index.mjs'

which reads like a broken checkout and is not.

If npm test fails with SlowBuffer is not defined

One dependency (avsc) still references a Node API removed years ago. The Dockerfile and CI patch it in place before running tests; locally, apply the same substitution to node_modules/avsc/lib/types.js, replacing new SlowBuffer with Buffer.alloc. There are two references in avsc@5.7.9.

Verifying an install

Point a real MCP client at it. That is the authoritative check, and the reason is this project's own most expensive lesson: raw JSON-RPC does no schema validation, so three releases once shipped with every tool carrying an empty inputSchema while hand-written probes reported success.

A one-line ping is still a useful container smoke test — it proves the image starts and answers:

echo '{"jsonrpc":"2.0","id":1,"method":"tools/list","params":{}}' \
  | docker run -i --rm ghcr.io/doublegate/cyberchef-mcp_v3:latest

Next: Client Setup.