passive_dns_lookup

ServerCVE MCP Server
CategoryRead

WHAT IT DOES

What passive_dns_lookup does on CVE MCP Server

AI agents call passive_dns_lookup to retrieve information from CVE MCP Server without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.

THE RISK

Low Risk

Why passive_dns_lookup needs a policy

This tool queries a passive DNS database to retrieve historical DNS resolution records. It performs a lookup operation that retrieves and returns data without creating, modifying, deleting, or executing any operations. The sole argument is a lookup target (ip_or_domain), and the output is informational DNS history. There are no side effects or state changes.

From the tool's definition Tool description states it 'Query[s] CIRCL Passive DNS' and 'Shows what hostnames have resolved to this IP, or what IPs a domain has pointed to.' These are read-only retrieval operations with no modification or execution capabilities.

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

POLICY

How to control passive_dns_lookup

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

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "passive_dns_lookup": {}
  }
}

passive_dns_lookup is read-only, so it stays allowed — but everything else on the server is denied unless you say otherwise.

Create a free account and register CVE 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.

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EXPLORE

Related tools and policies

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Go deeper

The MCP Attack Database → Documented attack patterns against MCP deployments — and the policies that stop them.
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Rate Limiting MCP Tool Calls: A Practical Guide →
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FAQ

Questions about passive_dns_lookup

What does the passive_dns_lookup tool do? +

Query CIRCL Passive DNS for historical DNS resolutions of an IP or domain. Shows what hostnames have resolved to this IP, or what IPs a domain has pointed to. Args: ip_or_domain: IPv4/IPv6 address or domain name to query. It is categorised as a Read tool in the CVE MCP Server MCP Server, which means it retrieves data without modifying state.

How do I enforce a policy on passive_dns_lookup? +

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

What risk level is passive_dns_lookup? +

passive_dns_lookup is a Read tool with low risk. Read-only tools are generally safe to allow by default.

Can I rate-limit passive_dns_lookup? +

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

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

passive_dns_lookup is provided by the CVE MCP Server MCP server (mukul975/cve-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 CVE MCP Server tool call.

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

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27 CVE MCP Server tools catalogued and risk-classified — across an index of 43,000+ MCP servers.