Individual skill

hunt-host-header

Hunt Host Header Injection — password reset poisoning → ATO, web cache poisoning via unkeyed Host/X-Forwarded-Host, routing-based SSRF (Host picks upstream → cloud metadata/internal services), path-override SSRF/ACL-bypass (X-Original-URL/X-Rewrite-URL), OAuth redirect_uri/issuer poisoning, and absolute-URL link poisoning in emails. High to Critical when it reaches ATO or mass cache poisoning. Built on public Host-header research (PortSwigger 'Practical web cache poisoning' + James Kettle, and the classic password-reset-poisoning class). Use on any forgot-password flow, CDN/reverse-proxy-fronted app, OAuth/OIDC endpoint, or absolute-URL-in-email feature.

skills/hunt-host-header/SKILL.md

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Nov 5, 2026
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Apache-2.0

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# HUNT-HOST-HEADER — Host Header Injection

## Grounding / Provenance

This skill is built from the public Host-header attack literature, not invented payloads.
Cite the *technique source* in your report, never a fabricated ID:

- **Password-reset poisoning class** — the canonical write-up is Skelet's/Detectify-era
  "Practical HTTP Host header attacks" (the Django `request.get_host()` → password-reset-link
  case). Many frameworks built the reset URL from the request Host with no `ALLOWED_HOSTS`-style
  allowlist. Cite the framework + the reflected-Host behaviour you actually observed.
- **Web cache poisoning via unkeyed Host / X-Forwarded-Host** — PortSwigger Research,
  James Kettle, "Practical Web Cache Poisoning" (2018) and "Web Cache Entanglement" (2020).
  These define unkeyed-input poisoning, which is the mechanism behind X-Forwarded-Host poisoning.