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Subdomain Finder MCP

io.github.theluckystrike/subdomain-finder-mcptheluckystrikestreamable-httpv1.0.0Scanned

Passive subdomain enumeration from certificate transparency (certspotter, crt.sh) with DNS checks.

4 tools: 4 only read.

Tools: 0 delete, 0 irreversible, 0 write, 4 read.
  • Reads private data · 1
  • Reads text others write · 4
  • Can send data out · 0
  • No findings

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Tools

Grouped by what each tool does, most consequential first. Open one for its reasons and full description; descriptions are the publisher's own words.

4 tools

Only reads 4Show 4 read-only tools
  • find_subdomainsPassive subdomain enumeration for a domain from live certificate transparency logs: certspotter (unexpired certificates) with crt.sh as fallback or for expired history.Reads text others writeNo findings

    Why it is in this group

    • The name "find_subdomains" says "find": a word for reading.

    What it can reach

    • untrusted-inputThe server marks it openWorldHint: true: it reaches things outside the server's own data.
    Description, as the server wrote it
    Passive subdomain enumeration for a domain from live certificate transparency logs: certspotter (unexpired certificates) with crt.sh as fallback or for expired history. Returns deduplicated hostnames with first seen and last seen issuance dates, certificate count, issuers and whether a wildcard certificate covers the name, plus the list of wildcard entries. Set resolve=true to also check the first 40 names with DNS over HTTPS and mark live hosts. Passive lookup of public certificate transparency logs; nothing is sent to the target. Use it on assets you own or are authorised to test.

    Annotations the server declares

    • title: Find subdomains
    • readOnlyHint: true
    • destructiveHint: false
    • idempotentHint: true
    • openWorldHint: true
  • get_certificate_historyCertificates logged in certificate transparency for one hostname (or a whole domain with include_subdomains): issuer organisation and DN, not_before and not_after dates, every SAN …Reads text others writeNo findings

    Why it is in this group

    • The name "get_certificate_history" says "get": a word for reading.

    What it can reach

    • untrusted-inputThe server marks it openWorldHint: true: it reaches things outside the server's own data.
    Description, as the server wrote it
    Certificates logged in certificate transparency for one hostname (or a whole domain with include_subdomains): issuer organisation and DN, not_before and not_after dates, every SAN on the certificate, revocation status and SHA-256 where certspotter has them. Summarises first and last issuance and the issuers used, which shows CA changes and renewal cadence. Default source certspotter (unexpired); include_expired uses crt.sh for the full history.

    Annotations the server declares

    • title: Certificate history
    • readOnlyHint: true
    • destructiveHint: false
    • idempotentHint: true
    • openWorldHint: true
  • resolve_subdomainsResolve up to 40 hostnames now through Cloudflare DNS over HTTPS (A, AAAA and the CNAME chain).Reads text others writeNo findings

    Why it is in this group

    • The name "resolve_subdomains" says "resolve": a word for reading.

    What it can reach

    • untrusted-inputThe server marks it openWorldHint: true: it reaches things outside the server's own data.
    • untrusted-inputThe description's first sentence says "resolve" and "http": it reads web pages, which anyone can write.
    Description, as the server wrote it
    Resolve up to 40 hostnames now through Cloudflare DNS over HTTPS (A, AAAA and the CNAME chain). Each host is marked live, nxdomain, no_records or dangling_cname (a CNAME whose target does not exist, a subdomain takeover lead), and CNAME targets on cloud platforms (S3, Azure, Heroku, GitHub Pages, Netlify, Vercel and others) are named. Also probes a random label per parent domain to detect wildcard DNS. DNS lookups only; no connection is made to the hosts.

    Annotations the server declares

    • title: Resolve subdomains
    • readOnlyHint: true
    • destructiveHint: false
    • idempotentHint: true
    • openWorldHint: true
  • summarize_attack_surfaceReads a domain's subdomains from live certificate transparency and groups them for recon triage: development and test, staging, admin and internal tools, APIs, authentication, mail…Reads private dataReads text others writeNo findings

    Why it is in this group

    • The name "summarize_attack_surface" says "summarize": a word for reading.

    What it can reach

    • private-dataThe description's first sentence says "read" and "mail": it reads mail.
    • untrusted-inputThe server marks it openWorldHint: true: it reaches things outside the server's own data.
    • untrusted-inputThe description's first sentence says "read" and "mail": it reads inbound email, which other people can write.
    Description, as the server wrote it
    Reads a domain's subdomains from live certificate transparency and groups them for recon triage: development and test, staging, admin and internal tools, APIs, authentication, mail, remote access (VPN), storage and CDN, legacy and backup. Each group has a count, examples and why it matters. Also returns naming clusters (for example *.eu.example.com), certificate issuers in use, wildcard entries and the 10 newest names. Passive only.

    Annotations the server declares

    • title: Attack surface summary
    • readOnlyHint: true
    • destructiveHint: false
    • idempotentHint: true
    • openWorldHint: true

This is not a safety rating, and no finding is not a safety guarantee. The groups and findings come from fixed checks of the tool definitions the server returned on the date shown, not from its code or what it does when called. How the checks work.

Exfil surface

Which tools read private data, which read text someone else can write, and which can send data out. One of each is a path a prompt injection can use.

No private-data, untrusted-input, outbound path in this server alone: no tool is tagged outbound.

Reads private data1
Reads files, mail, messages, databases, secrets, calendars or repositories.
Reads text others write4
Brings in text someone else can write: web pages, inbound email, messages, issues and comments.
Can send data out0
Can carry data to people or systems: it sends, posts or publishes, or takes a recipient, channel or URL.

Other servers in the same agent add their own tools to these paths. Audit your whole setup to see them together.

Findings

Matches of fixed checks, with the text they matched.

No check matched anything in these tool definitions. That is not a safety guarantee.

History

Changes to its tool definitions and to its remote endpoint, newest first.

No change seen yet. Its tools are rescanned every day, and a remote endpoint is looked at once a week.

All changes to this server

Install

Pinned to version 1.0.0. Values in angle brackets are yours to fill in.

claude mcp add --transport http subdomain-finder https://subdomain-finder-mcp.lipmichal.workers.dev/mcp
claude mcp add --transport http subdomain-finder https://subdomain-finder-mcp.lipmichal.workers.dev/mcp

Run in a terminal.

Claude Code permissions

Allow the reads, ask before a change or a way out, deny the deletes. Paste into .claude/settings.json.

.claude/settings.json
{
  "permissions": {
    "allow": [
      "mcp__subdomain-finder__find_subdomains",
      "mcp__subdomain-finder__resolve_subdomains",
      "mcp__subdomain-finder__get_certificate_history",
      "mcp__subdomain-finder__summarize_attack_surface"
    ],
    "ask": [],
    "deny": []
  }
}

Tools that only read are allowed, tools that change things ask first, tools that delete or cancel are denied. A read that can send data out (it takes a URL, say) asks first too. It assumes the server is installed as subdomain-finder. Review it before you use it.

Capability tags behind 4 rules
  • mcp__subdomain-finder__find_subdomains untrusted-input
  • mcp__subdomain-finder__resolve_subdomains untrusted-input
  • mcp__subdomain-finder__get_certificate_history untrusted-input
  • mcp__subdomain-finder__summarize_attack_surface private-data, untrusted-input

Pin

Keep the decision: fail CI when the tools change, follow every change, or show a badge.

Pin in CI

Fail a build when the tools you reviewed are not the tools the server serves today.

curl -s "https://anlyon.dev/api/v1/servers/io.github.theluckystrike/subdomain-finder-mcp/verify?hash=fa8abae33dd5a47de2b31a585ab5b8103eafae0aeb9230e40b8564f198b626fb" | jq -e '.changed == false'

Pinned hash fa8abae33dd5, from Nov 2, 2026, 03:18 UTC.

Watch

Get told when its tools change: a new tool, a new description, a new class.

https://anlyon.dev/servers/io.github.theluckystrike/subdomain-finder-mcp/changes.xml

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Source: MCP Registry · repository. Synced Nov 2, 2026, 03:18 UTC.