submit_flag · CTFd MCP Server MCP: Risk & Policy

WHAT IT DOES

What submit_flag does on CTFd MCP Server

AI agents use submit_flag to create or update resources in CTFd MCP Server — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your CTFd MCP Server environment.

WHY IT NEEDS A POLICY

Why submit_flag needs a policy

This tool modifies state by recording a flag submission, which changes user progress, scores, and competition standings. While not destructive (reversible; a wrong submission doesn't erase data), it creates/writes a new record. The high severity reflects the potential for an AI agent to spam incorrect submissions, manipulate leaderboards, or interfere with competition integrity.

From the tool's definition Tool named 'submit_flag' in a CTFd (Capture The Flag) server context. CTFd is a platform for running security competitions where flag submission is the primary competitive action that records attempts and progression.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

submit_flag Rate-limited

submit_flag stays usable, but capped — an agent stuck in a loop can't make hundreds of changes a minute. Everything else on the server is denied unless you say otherwise.

View as policy code

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "submit_flag": {
      "limits": [
        {
          "counter": "submit_flag_rate",
          "window": "minute",
          "max": 30,
          "scope": "grant"
        }
      ]
    }
  }
}

LIMIT THIS TOOL →

Instant setup, no code required.

PolicyLayer is an MCP gateway: every tool call is checked against your rule before it reaches CTFd MCP Server, so you can run agents against it safely.

FAQ

Questions about submit_flag

What does the submit_flag tool do? +

submit_flag. It is categorised as a Write tool in the CTFd MCP Server MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on submit_flag? +

Register the CTFd MCP Server MCP server in PolicyLayer and add a rule for submit_flag: 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 CTFd MCP Server. Nothing to install.

What risk level is submit_flag? +

submit_flag is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.

Can I rate-limit submit_flag? +

Yes. Add a rate_limit block to the submit_flag 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 submit_flag completely? +

Set action: deny in the PolicyLayer policy for submit_flag. 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 submit_flag? +

submit_flag is provided by the CTFd MCP Server MCP server (mrjamescot/ctfd-mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.