disable_regex · Firegex MCP: Risk & Policy

WHAT IT DOES

What disable_regex does on Firegex

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

WHY IT NEEDS A POLICY

Why disable_regex needs a policy

The tool modifies rule configuration state in a persistent store (database) but preserves the rule itself, making it reversible (can be re-enabled). This is neither destructive (rule is not deleted) nor execute (no code execution or external operation triggered). Context: Firegex is a firewall, so disabling rules could have network-wide blast radius affecting traffic filtering, elevating severity beyond low.

From the tool's definition disable_regex disables a regex rule (kept in database, not applied). The description indicates modification of a stored rule's active state without deletion, which is reversible. This aligns with Write: creates or modifies data reversibly.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

disable_regex Rate-limited

disable_regex 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": {
    "disable_regex": {
      "limits": [
        {
          "counter": "disable_regex_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 Firegex, so you can run agents against it safely.

FAQ

Questions about disable_regex

What does the disable_regex tool do? +

Disable a regex (kept in DB, not applied). It is categorised as a Write tool in the Firegex MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on disable_regex? +

Register the Firegex MCP server in PolicyLayer and add a rule for disable_regex: 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 Firegex. Nothing to install.

What risk level is disable_regex? +

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

Can I rate-limit disable_regex? +

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

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

disable_regex is provided by the Firegex MCP server (umbra2728/firegex-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.