Borrowing it
Nothing to install: this file belongs to Sanoy24/safe-fetch-mcp-server. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.
curl -O https://raw.githubusercontent.com/Sanoy24/safe-fetch-mcp-server/main/.claude/skills/secure-fetch-ssrf/SKILL.mdgit clone --depth 1 https://github.com/Sanoy24/safe-fetch-mcp-serverWrote 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/sanoy24/safe-fetch-mcp-server/secure-fetch-ssrf)<a href="https://agentmods.dev/skills/sanoy24/safe-fetch-mcp-server/secure-fetch-ssrf"><img src="https://agentmods.dev/badge/skills/sanoy24/safe-fetch-mcp-server/secure-fetch-ssrf/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/sanoy24/safe-fetch-mcp-server/secure-fetch-ssrf"><img src="https://agentmods.dev/badge/skills/sanoy24/safe-fetch-mcp-server/secure-fetch-ssrf.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 | $0.01210 |
| Opus 5 | $0.00027 | $0.00605 |
| Sonnet 5 | $0.00011 | $0.00242 |
| Haiku 4.5 | $0.00005 | $0.00121 |
Grade B, and why
secure-fetch-ssrf 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 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.
Cloud metadata endpointmediumServer-side request forgery
One request to 169.254.169.254 can return temporary IAM credentials.
| 1 | Cloud metadata SSRF | `http://169.254.169.254/latest/meta-data/` | Block link-local `169.254.0.0/16` on resolved IP | Downgraded: this mod is about security review, or the phrase is quoted, so it is likely naming the pattern rather than instructing it.
How it starts
The opening of the file, as written. The whole thing — 77 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Secure Fetch / SSRF Defense
This is the security contract. If you change anything that touches URLs, DNS, the HTTP client, or redirects, re-read this and keep every invariant.
Core principle
Allowlist-first, validate the resolved IP, pin the connection. Hostname string checks and blocklists fail: IP encodings are effectively infinite and hostnames can rebind. The only reliable model is: resolve → validate the resolved IP against explicit ranges → connect to that same IP → re-validate on every redirect.
Threat → defense matrix
| # | Attack | Example | Defense |
|---|---|---|---|
| 1 | Cloud metadata SSRF | http://169.254.169.254/latest/meta-data/ |
Block link-local 169.254.0.0/16 on resolved IP |
| 2 | Private-range SSRF | http://10.0.0.5, http://192.168.1.1 |
Block RFC-1918 on resolved IP |
| 3 | Loopback | http://127.0.0.1, http://127.1 |
Block 127.0.0.0/8 after normalization |
| 4 | IPv4-mapped IPv6 loopback | http://[::ffff:127.0.0.1] |
Normalize IPv6, unwrap mapped IPv4, then range-check |
| 5 | IPv6 loopback / ULA | http://[::1], fc00::/7 |
Block on resolved IPv6 |
| 6 | Encoding bypass | octal/hex/decimal/dotless IPs | Validate the resolved IP, not the string |
| 7 | DNS rebinding | resolves public then private | Resolve once, pin the connection to that IP |
| 8 | Redirect-to-internal | 302 → http://127.0.0.1 |
Re-run full validation on every hop |
| 9 | Non-HTTP schemes | file://, gopher://, ftp:// |
Scheme allowlist: http, https only |
| 10 | Credentials in URL | http://user:pass@host |
Strip / reject userinfo |
| 11 | Resource exhaustion | multi-GB body, slow-loris | Max-bytes cap + connect/idle/total timeouts |
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.
- 10d ago First seen · 77 lines · 54 tokens per session scan B 6c1654336f67
secure-fetch-ssrf is a skill published in the GitHub repository Sanoy24/safe-fetch-mcp-server (1 stars, last pushed 1mo ago), licensed MIT. It adds 54 tokens to every session and 1,210 once invoked, about $0.0003 per session on Opus 5. A static security scan graded it B with 1 finding (cloud metadata endpoint). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.
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