| name | waf-bypass |
| description | Systematic, tiered 403/WAF bypass decision guide plus common curl error diagnosis. Converted from master-pentest-prompt.md Phase 0.6. Use whenever a request comes back 403/blocked, or tool_resolver.classify_block() flags a WAF signature. |
403 / WAF bypass master guide
When to use
A 403 appears, or mcp-servers/tool_resolver.py's classify_block()
returns "waf" on a tool's output. Work the tiers in order before giving
up on a blocked endpoint you actually need to test.
Tiers 1-4 below are automated by mcp-servers/waf-bypass-mcp's
attempt_bypass(url, baseline_status, tiers) -- call that first rather
than hand-crafting each variant; it runs all of them in one call and
reports which (if any) changed the response. This skill documents what
it's actually doing, plus Tier 5, which isn't automated (it needs
external OSINT, not a retry loop).
Tier 1 -- Header manipulation
- Fake client IP:
X-Forwarded-For / X-Real-IP / X-Originating-IP /
X-Remote-IP / X-Client-IP / X-Custom-IP-Authorization /
X-ProxyUser-Ip / True-Client-IP / Forwarded: for=127.0.0.1;host=localhost
-- set to 127.0.0.1/localhost on the blocked endpoint.
- Fake
Host: localhost, 127.0.0.1, internal.<domain>.
- UA spoofing: Googlebot, Bingbot, empty UA.
Tier 2 -- Path manipulation
URL-encode letters (%61dmin), %2f for /, trailing space/tab/null,
--path-as-is with ./, /., //, /../, %2e; case variations
(Admin, ADMIN); extension append (.json/.html/.php/;.js/#).
Tier 3 -- Method switching
POST/PUT/PATCH/OPTIONS/TRACE/HEAD/CONNECT plus method
override headers (X-HTTP-Method-Override, X-Method-Override,
_method=).
Tier 4 -- HTTP version tricks
--http1.0/--http1.1, --http2, --http2-prior-knowledge.
Tier 5 -- CDN/Cloudflare origin bypass (not automated)
Find the origin IP (SecurityTrails/Shodan/Censys/CT logs), then
--resolve <domain>:443:<IP> or -H "Host: <domain>" straight to the
IP; spoof CF-Connecting-IP/CF-IPCountry; reuse cf_clearance if
known. This needs real OSINT lookups per target, not a retry loop, which
is why waf-bypass-mcp doesn't automate it.
Decision logic
Still 403 after all tiers -> document the host as WAF-protected and move
on. If the target is heavily WAF-protected, research current WAF-bypass
techniques for that specific vendor online, apply them; if bypass still
fails, move on rather than looping.
Diagnosing curl errors
| curl error | Meaning | Fix |
|---|
| (6) DNS | Couldn't resolve host | --dns-servers 8.8.8.8 |
| (7) port closed | Connection refused | try 80/8080/8443 |
| (35) SSL | SSL handshake failed | -k / --tlsv1.2 |
| (52) empty reply | Server closed connection | --http1.1 |
| (56) recv failure | Receive error | retry with delay + a legit UA |
