Affected: Flux159 mcp-server-kubernetes

mcp-server-kubernetes is a Model Context Protocol server for Kubernetes cluster management. Versions 3.4.0 and prior contain an argument injection vulnerability in the port_forward tool in src/tools/port_forward.ts, where a kubectl command is constructed via string concatenation with user-controlled input and then naively split on spaces before being passed to spawn(). Unlike all other tools in the codebase which correctly use array-based argument passing with execFileSync(), port_forward treats every space in user-controlled fields (namespace, resourceType, resourceName, localPort, targetPort) as an argument boundary, allowing an attacker to inject arbitrary kubectl flags. This enables exposure of internal Kubernetes services to the network by injecting --address=0.0.0.0, cross-namespace targeting by injecting additional -n flags, and indirect exploitation via prompt injection against AI agents connected to the MCP server. This issue has been fixed in version 3.5.0.

Affected: npm: mcp-server-kubernetes

## Summary

The `port_forward` tool in `mcp-server-kubernetes` constructs a kubectl command as a string and splits it on spaces before passing to `spawn()`. Unlike all other tools in the codebase which correctly use `execFileSync("kubectl", argsArray)`, `port_forward` uses string concatenation with user-controlled input (`namespace`, `resourceType`, `resourceName`, `localPort`, `targetPort`) followed by naive `.split(" ")` parsing. This allows an attacker to inject arbitrary kubectl flags by embedding spaces in any of these fields.

## Affected Versions

`<= 3.4.0`

## Vulnerability Details

**File:** `src/tools/port_forward.ts` (compiled: `dist/tools/port_forward.js`)

The `startPortForward` function builds a kubectl command string by concatenating user-controlled input:

```javascript let command = `kubectl port-forward`; if (input.namespace) { command += ` -n ${input.namespace}`; } command += ` ${input.resourceType}/${input.resourceName} ${input.localPort}:${input.targetPort}`; ```

This string is then split on spaces and passed to `spawn()`:

```javascript async function executeKubectlCommandAsync(command) { return new Promise((resolve, reject) => { const [cmd, ...args] = command.split(" "); const process = spawn(cmd, args); ```

Because `.split(" ")` treats every space as an argument boundary, an attacker can inject additional kubectl flags by embedding spaces in any of the user-controlled fields.

### Contrast with other tools

Every other tool…