How do I install the Web Host Header skill?

Run npx skillmds@latest add noorqureshi/web-host-header in your terminal (requires Node.js), paste this page's agent-chat prompt into Claude, Cursor, or any MCP-connected agent, or download the SKILL.md file and copy it into your agent's skills directory.

Is Web Host Header safe to use?

This skill has not completed SkillMD's automated safety review yet. SkillMD never runs a skill's scripts for you; review the SKILL.md before installing.

Which AI agents work with Web Host Header?

This skill is tagged as working with Claude Code, Claude.ai, OpenAI Codex. SKILL.md is an open format, so most agents that read a skills directory can load it too.

Is Web Host Header free to use?

Yes. Installing skills from SkillMD is free, and the skill stays under its author's original license.

Who published Web Host Header?

NoorQureshi (@noorqureshi) published this skill. Their other Agent Skills are listed on their SkillMD profile.

Web Host Header by noorqureshi — Agent Skill

Name: Web Host Header
Author: NoorQureshi

Web Host Header

Host header injection — abuse a trusted Host/X-Forwarded-Host to poison password-reset links, routing, and caches. Load when the app builds absolute URLs from the request host, on password-reset flows, or behind a proxy/CDN. Signals: reset emails with links, X-Forwarded-Host reflected, virtual hosting, cache in front.

NoorQureshi ce44881 2.2 KB Updated Sep 17, 2026

File contents

Host header injection

When it applies

The server trusts the Host (or X-Forwarded-Host) header to build absolute URLs, decide routing, or key a cache. Classic impact: password-reset poisoning (the reset link points at your domain, so the victim's token comes to you).

Why it works

Frameworks read the request host to construct links (https://{host}/reset?token=…). The host is attacker-controlled, so if it isn't validated against an allowlist, you control where generated links point — and where secrets in them land.

Method

Reset poisoning: trigger a password reset for a victim; intercept and set Host: attacker.com (or add X-Forwarded-Host: attacker.com). If the emailed link uses your host, the victim's click sends their reset token to you → account takeover.
Routing/authz: try Host: of an internal vhost (admin.internal) to reach restricted apps behind the proxy; test X-Forwarded-Host, X-Forwarded-Server, X-Host, dup Host headers.
Cache poisoning: if the host is reflected into a cached response, combine with web-cache-poisoning to serve your host to other users.
Validation bypass: absolute-URL Host (Host: attacker.com), Host: victim.com:@attacker.com, line-wrapping, and duplicate headers (front-end vs back-end pick different ones).

Gotchas

Many stacks now validate Host — confirm the generated link/response actually uses your value.
X-Forwarded-Host often wins even when Host is validated — always test it separately.
Reset poisoning needs the app to email a host-derived link; verify by reading the email/link.

Verify success

A password-reset (or other) link built with your attacker host, or an internal vhost reached, or a poisoned cached response served to a clean request.

References

PortSwigger Host header attacks labs; OWASP host-header injection.

---name: web-host-headerdescription: Host header injection — abuse a trusted Host/X-Forwarded-Host to poison password-reset links, routing, and caches. Load when the app builds absolute URLs from the request host, on password-reset flows, or behind a proxy/CDN. Signals: reset emails with links, X-Forwarded-Host reflected, virtual hosting, cache in front.---# Host header injection## When it appliesThe server trusts the `Host` (or `X-Forwarded-Host`) header to build absolute URLs, deciderouting, or key a cache. Classic impact: password-reset poisoning (the reset link points at yourdomain, so the victim's token comes to you).## Why it worksFrameworks read the request host to construct links (`https://{host}/reset?token=…`). The host isattacker-controlled, so if it isn't validated against an allowlist, you control where generatedlinks point — and where secrets in them land.## Method1. **Reset poisoning**: trigger a password reset for a victim; intercept and set `Host: attacker.com` (or add `X-Forwarded-Host: attacker.com`). If the emailed link uses your host, the victim's click sends their reset token to you → account takeover.2. **Routing/authz**: try `Host:` of an internal vhost (`admin.internal`) to reach restricted apps behind the proxy; test `X-Forwarded-Host`, `X-Forwarded-Server`, `X-Host`, dup Host headers.3. **Cache poisoning**: if the host is reflected into a cached response, combine with `web-cache-poisoning` to serve your host to other users.4. **Validation bypass**: absolute-URL Host (`Host: attacker.com`), `Host: victim.com:@attacker.com`, line-wrapping, and duplicate headers (front-end vs back-end pick different ones).## Gotchas- Many stacks now validate Host — confirm the generated link/response actually uses your value.- `X-Forwarded-Host` often wins even when `Host` is validated — always test it separately.- Reset poisoning needs the app to email a host-derived link; verify by reading the email/link.## Verify successA password-reset (or other) link built with your attacker host, or an internal vhost reached, ora poisoned cached response served to a clean request.## ReferencesPortSwigger Host header attacks labs; OWASP host-header injection.

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