This tweet by @pyn3rd discusses a method for bypassing Web Application Firewalls (WAFs) by combining encoding bypass techniques with boundary confusion. The key idea is that WAFs, which protect web applications from attacks by filtering malicious inputs, can be evaded when the attacker encodes their payload in a way that the WAF does not properly decode or interpret, and simultaneously creates confusion around data boundaries (such as input delimiters or markers). This combination can trick the WAF into missing or misinterpreting the attack, allowing the malicious payload to pass through undetected. This method can potentially apply broadly, affecting various types of vulnerabilities, since it concerns how data is parsed and filtered rather than a specific attack type. Although the tweet does not specify the exact WAF vendor or a concrete payload, the principle highlights a common weakness in WAFs related to input normalization and parsing. Understanding and mitigating such bypass techniques requires careful handling of input encoding and thorough boundary checks in WAF rules.
For more insights, check out the original tweet here: https://twitter.com/tech_maddy/status/1999081635439050845