This tweet highlights a method to bypass a Web Application Firewall (WAF) rule designed to block Server-Side Request Forgery (SSRF) attacks. SSRF is a vulnerability where an attacker can make the server perform unauthorized requests to internal or external resources. The bypass specifically targets rules blocking access to internal URLs. The tweet mentions that certain URL formats are accepted by the WAF despite attempting to block internal access. Specifically, using the hexadecimal notation for the localhost address (https://0x7f000001/) and the IPv6 loopback address (https://[::1]/) can bypass the WAF rules. This technique tricks the WAF into not recognizing these URLs as internal addresses, allowing the attacker to reach sensitive internal resources. Such bypasses are useful for bug bounty hunters as they reveal weaknesses in the WAF's filtering logic. Understanding these payloads helps in creating more robust WAF rules to better protect against SSRF attacks.
Original tweet: https://twitter.com/momika233/status/2033572791002247368