Getting it into your agent
One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.
npx skills add miru-zero/zero-brain --skill http-host-header-attacksgit clone --depth 1 https://github.com/miru-zero/zero-brainWrote 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.
[](https://agentmods.dev/skills/miru-zero/zero-brain/http-host-header-attacks)<a href="https://agentmods.dev/skills/miru-zero/zero-brain/http-host-header-attacks"><img src="https://agentmods.dev/badge/skills/miru-zero/zero-brain/http-host-header-attacks/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.
<a href="https://agentmods.dev/skills/miru-zero/zero-brain/http-host-header-attacks"><img src="https://agentmods.dev/badge/skills/miru-zero/zero-brain/http-host-header-attacks.svg" alt="Reviewed on agentmods" width="80" height="20"></a>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.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00054 | $0.02914 |
| Opus 5.5 | $0.00022 | $0.01166 |
| Sonnet 5.5 | $0.00011 | $0.00583 |
| Haiku 4.5 | $0.00005 | $0.00291 |
Grade B, and why
http-host-header-attacks scanned grade B with 1 finding 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 1mo 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.
Cloud metadata endpointmediumServer-side request forgery
One request to 169.254.169.254 can return temporary IAM credentials.
│ └── Host: 169.254.169.254 → cloud metadata? Downgraded: this mod is about security review, or the phrase is quoted, so it is likely naming the pattern rather than instructing it.
This is a copy
97% identical to http-host-header-attacks — 7 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.
How it starts
The opening of the file, as written. The whole thing — 321 lines — stays where its author put it; the contents beside it link to each section on GitHub.
SKILL: HTTP Host Header Attacks — Injection & Routing Abuse
AI LOAD INSTRUCTION: Covers Host header injection for password reset poisoning, cache poisoning, SSRF via routing, and virtual host bypass. Includes bypass techniques for Host validation and framework-specific behaviors. Base models often miss the double-Host trick, absolute-URI override, and connection-state attacks.
0. RELATED ROUTING
- web-cache-deception when Host injection is combined with cache behavior
- ssrf-server-side-request-forgery when Host header routes requests to internal services
- open-redirect when Host injection causes redirect to attacker domain
- waf-bypass-techniques when Host manipulation helps bypass WAF routing
- request-smuggling when smuggling enables Host header manipulation past front-end validation
- subdomain-takeover when Host routing exposes internal vhosts resolvable via subdomain
1. ATTACK SURFACE
The Host header is used by web applications and infrastructure for:
| Usage | Exploitation |
|---|---|
| URL generation (password reset links, email links) | Inject attacker domain → user clicks link to attacker |
| Virtual host routing | Spoof Host → access internal/admin vhost |
| Cache key component | Inject different Host → poison cache for all users |
| Reverse proxy routing | Host determines backend → SSRF to internal services |
| Access control decisions | Host-based ACLs can be bypassed |
| Canonical URL / SEO redirects | Host injection → open redirect |
2. PASSWORD RESET POISONING
The most common and impactful Host header attack.
How It Works
1. Attacker requests password reset for [email protected]
2. Attacker modifies Host header in the reset request:
POST /forgot-password HTTP/1.1
Host: attacker.com ← injected
[email protected]
3. Server generates reset link using Host header value:
"Click here to reset: https://attacker.com/reset?token=SECRET_TOKEN"
4. Victim receives email, clicks link → token sent to attacker
5. Attacker uses token on real target.com to reset password
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.
- 1mo ago First seen · 321 lines · 54 tokens per session scan B 42e4fb91bb29
http-host-header-attacks is a skill published in the GitHub repository miru-zero/zero-brain (0 stars, last pushed 2mo ago), licensed MIT. It adds 54 tokens to every session and 2,914 once invoked, about $0.0002 per session on Opus 5.5. A static security scan graded it B with 1 finding (cloud metadata endpoint). It is 97% identical to http-host-header-attacks, differing in 7 lines, and is treated as a copy.
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