run_custom_command

THE RISK

High Risk

Why run_custom_command needs a policy

A tool that executes custom commands in a privileged Docker container has the highest blast radius: arbitrary code execution with root or elevated privileges in an isolated but fully operational Linux environment. This allows an AI agent to run any shell command, modify system state, exfiltrate data, or chain attacks.

From the tool's definition Tool name 'run_custom_command' with empty description in a Kali Linux MCP server context that 'enabling network scanning (nmap), web vulnerability scanning (nikto), and custom command execution.' The server description explicitly mentions 'custom command…

Documented attack patterns abuse exactly the kind of access run_custom_command gives an agent:

POLICY

How to control run_custom_command

PolicyLayer is an MCP gateway — it sits between your AI agents and Kali Linux MCP Server, and nothing reaches the server without passing your rules. This is the rule we recommend for run_custom_command:

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "run_custom_command": {
      "limits": [
        {
          "counter": "run_custom_command_rate",
          "window": "minute",
          "max": 10,
          "scope": "grant"
        }
      ]
    }
  }
}

run_custom_command stays usable, but rate-capped — a runaway agent can't fire it dozens of times a minute. Everything else on the server is denied unless you say otherwise.

Create a free account and register Kali Linux MCP Server — nothing to install.
Add this policy — paste it, or build it visually.
Point your MCP client (Claude, Cursor, anything) at your gateway URL.

RATE-LIMIT THIS TOOL →

Free to start. No card required.

EXPLORE

Related tools and policies

More Kali Linux MCP Server tools

Execute nikto_scan nikto_scan Execute nmap_scan nmap_scan Execute simple_port_scan Simple TCP port scanner that doesn't require special privileges. Execute whatweb_scan Identify web technologies with WhatWeb. Read check_container_permissions Check if the container is running with necessary privileges for security tools. Read list_available_tools List security tools available in this Kali Linux container.

All 7 Kali Linux MCP Server tools →

Execute tools on other servers

Android Forensics ADB MCP Server adb_shell_command EMBA-MCP run_emba_scan Frida Game Hacking MCP remove_breakpoint Procmon request_elevation

Go deeper

High-risk tools in Kali Linux MCP Server → Every high-risk tool this server exposes, in one view.
All high-risk MCP tools → Every high-risk tool across the catalogue, and the policy pattern that contains them.
The MCP Attack Database → Documented attack patterns against MCP deployments — and the policies that stop them.
Agent sandbox → Bounding what an agent can execute and where the boundary should sit.
Least privilege for MCP → Granting agents the minimum tool surface the task needs.
Rate Limiting MCP Tool Calls: A Practical Guide →
MCP Security: Why Prompt Guardrails Aren't Enough →

FAQ

Questions about run_custom_command

What does the run_custom_command tool do? +

run_custom_command. It is categorised as a Execute tool in the Kali Linux MCP Server MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

How do I enforce a policy on run_custom_command? +

Register the Kali Linux MCP Server MCP server in PolicyLayer and add a rule for run_custom_command: allow, deny, rate-limit, or require approval. Point your MCP client at the PolicyLayer proxy URL and the rule is enforced on every call, before it reaches Kali Linux MCP Server. Nothing to install.

What risk level is run_custom_command? +

run_custom_command is a Execute tool with high risk. Execute tools should be rate-limited and have argument validation enabled.

Can I rate-limit run_custom_command? +

Yes. Add a rate_limit block to the run_custom_command rule in your PolicyLayer policy. For example, setting max: 10 and window: 60 limits the tool to 10 calls per minute. Rate limits are tracked per agent session and reset automatically.

How do I block run_custom_command completely? +

Set action: deny in the PolicyLayer policy for run_custom_command. The AI agent will receive a policy violation error and cannot call the tool. You can also include a reason field to explain why the tool is blocked.

What MCP server provides run_custom_command? +

run_custom_command is provided by the Kali Linux MCP Server MCP server (marklechner/kali-mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

Enforce policy on every Kali Linux MCP Server tool call.

Start from Kali Linux MCP Server, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.

CHECK YOUR STACK →