vhost-enumeration

vhost-enumeration is a skill for Claude Code, Codex from uphiago/recon-skills. It costs 20 tokens per session (1,571 once invoked), scanned B, original, MIT.

A method for finding hidden websites hosted on the same IP address by testing different Host headers and reading domain names listed in SSL certificates.

In plain words
What is it for?
It helps map virtual hosts, uncover services behind reverse proxies, and identify additional hostnames for authorized security testing.
Why use it?
Normal subdomain searches can miss internal sites, development systems, and admin panels that share an IP address but only answer to specific hostnames.

Skill for Claude CodeCodex

Written for no agent in particular: nothing here depends on one.

Needs its repository: it runs a file that does not travel with it, so clone the repository first. The line is cat found_vhosts.txt | gowitness file -f - --no-http -P ./vhost_screenshots/.

Good fit It helps map virtual hosts, uncover services behind reverse proxies, and identify additional hostnames for authorized security testing.

Compare 6 skills from other repositories ↓
About the project

Recon Skills is a pack of security-testing skills covering reconnaissance, web applications, APIs, authentication, vulnerability validation, cloud infrastructure, and reporting. Security professionals use it for authorized assessments of systems they own or have written permission to test. The catalogue entries are individual skills from the pack.

uphiago/recon-skills · 1,251 stars · on GitHub · hiago.sh

Install

Getting it into your agent

It runs from inside its repository, so the clone comes first — what it calls does not travel with the file alone.

Clone the repo
git clone --depth 1 https://github.com/uphiago/recon-skills
agentmods
npx agentmods add skills/uphiago/recon-skills/vhost-enumeration

Made for: Claude Code, Codex.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for vhost-enumeration

README.md
[![agentmods](https://agentmods.dev/badge/skills/uphiago/recon-skills/vhost-enumeration/github.svg)](https://agentmods.dev/skills/uphiago/recon-skills/vhost-enumeration)
Your own site
<a href="https://agentmods.dev/skills/uphiago/recon-skills/vhost-enumeration"><img src="https://agentmods.dev/badge/skills/uphiago/recon-skills/vhost-enumeration/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

agentmods 80×15 button for vhost-enumeration

Your own site · 80×15
<a href="https://agentmods.dev/skills/uphiago/recon-skills/vhost-enumeration"><img src="https://agentmods.dev/badge/skills/uphiago/recon-skills/vhost-enumeration.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 20 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,571 The whole file, excluding the scripts and references it only reads on demand.
Security scan B 2 findings. A grade says what 26 rules found in the file — not that it is safe. Third-party audits
  • NVIDIA SkillSpector warn 7 Sept 2026
SkillSpector: 2 findings, up to high

These are SkillSpector’s own severities. On a checked sample its high-severity flags on skills were ~96% false positives — a documented command, a public API, a “never do X” rule — so we show them as a caution to read, not a verdict. Why →

  • high Tool Misuse · line 96
    Tool calls are chained to bypass individual safety checks or escalate capabilities beyond what any single tool call would allow.
    Fix: Limit tool chaining depth and validate the output of each tool before passing it to the next. Require explicit user approval for multi-step chains.
  • medium Privilege Escalation · line 96
    Commands invoke sudo or root privileges. Verify this elevated access is necessary and justified.
    Fix: Avoid sudo/root unless strictly required. Prefer least-privilege patterns. If elevation is needed, document the justification and scope.
How audits are shown
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5.1 $0.00020 $0.01571
Opus 5 $0.00010 $0.00785
Sonnet 5 $0.00004 $0.00314
Haiku 4.5 $0.00002 $0.00157

Measured 10d ago against content hash b895d07f06f3, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-09, from the pricing page.

Security

Grade B, and why

vhost-enumeration scanned grade B with 2 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 10d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Asks for rootmediumPrivilege escalation

A mod that escalates privileges can change anything on the machine, not only the project.

echo "TARGET_IP dev.target.com internal.target.com admin.target.com" | sudo tee -a /etc/hosts

Makes network callslowCapability

Not a fault in itself. Listed so you know the mod talks to something, and to what.

compatibility: Requires curl, ffuf, dnsx
recon/vhost-enumeration/SKILL.md · 167 lines

How it starts

The opening of the file, as written. The whole thing — 167 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Virtual Host Enumeration

Discover hidden virtual hosts on IP addresses by fuzzing the Host header. Many servers only respond to specific domain names and remain invisible to standard subdomain enumeration. VHOST fuzzing exposes internal services, development environments, and admin panels that share the same IP but answer to different hostnames.

When to Use

  • You have a list of target IPs from skill_view(name='origin-ip-discovery') or skill_view(name='port-service-discovery').
  • A server returns default/blank pages for unknown Host headers.
  • Subdomain enumeration may have missed internal-only hostnames.
  • SSL certificates on an IP list multiple domain names in the SAN field.
  • You need to map internal services behind a reverse proxy.

Prerequisites

  • terminal with curl, ffuf, dnsx, and httpx.
  • A DNS wordlist for hostname fuzzing.
  • A list of target IP addresses.

Quick Detection

# Basic VHOST fuzz on a single IP
ffuf -u http://TARGET_IP \
  -w /path/to/wordlist.txt \
  -H "Host: FUZZ.target.com" \
  -fs 0 -mc 200,301,302,401,403

Procedure

Phase 1 — Host Header Fuzzing

# Fuzz for virtual hosts matching the target domain pattern
ffuf -u http://TARGET_IP \
  -w $DNS_WORDLIST \
  -H "Host: FUZZ.target.com" \
  -fs DEFAULT_RESPONSE_SIZE \
  -mc 200,301,302,401,403 \
  -o vhost_ffuf.json

# HTTPS variant
ffuf -u https://target.com \
  -w $DNS_WORDLIST \
  -H "Host: FUZZ.target.com" \
  -mc 200,301,302,401,403

# Fuzz multiple IPs with a wordlist
cat unique_ips.txt | while read ip; do
  ffuf -u "http://$ip" \
    -w $DNS_WORDLIST \
    -H "Host: FUZZ.target.com" \
    -fs 0 -mc 200,301,302 -o "vhost_$ip.json"
  sleep 0.5
done

Phase 2 — Response Filtering

# Auto-calibrate: ffuf detects default response size and filters it out
ffuf -u http://TARGET_IP \
  -w $DNS_WORDLIST \
  -H "Host: FUZZ.target.com" \
  -ac -sf -s \
  -mc 200

# Manual calibration: find the default response size first
curl --max-time 30 --connect-timeout 10 -s http://TARGET_IP -H "Host: nonexistentxxxxx12345.target.com" | wc -c
# Use that size as -fs filter

Read the full file on GitHub · 167 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 10d ago First seen · 167 lines · 20 tokens per session scan B b895d07f06f3

Subscribe to this mod's changes

vhost-enumeration is a skill published in the GitHub repository uphiago/recon-skills (1,251 stars, last pushed 8d ago), licensed MIT. It adds 20 tokens to every session and 1,571 once invoked, about $0.0001 per session on Opus 5. A static security scan graded it B with 2 findings (asks for root, makes network calls). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

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