This tweet highlights a clever way to bypass Web Application Firewall (WAF) signatures using the UTF-16LE encoding engine. While the specific WAF vendor is not mentioned, this bypass technique can affect multiple types of vulnerabilities because it manipulates how the payload is encoded before inspection by the WAF. UTF-16LE encoding transforms the payload into a different byte sequence that might not be detected by normal signature checks of the WAF. This method can be particularly effective against WAFs that do not properly decode or normalize UTF-16LE encoded input before applying their security rules.
The tweet refers to a GitHub page where detailed information and implementation are shared. This suggests that the bypass involves encoding the malicious payload in UTF-16LE format to evade detection and filtering by WAFs. Security researchers and penetration testers can study this approach to understand the limitations of current WAF signature engines and to improve WAF designs to handle different encodings comprehensively.
In summary, using UTF-16LE encoding to bypass WAF signatures is a universal technique that can circumvent detection by altering the byte representation of payloads, which can help in bypassing multiple vulnerability protections such as XSS, SQLi, or RCE depending on the input filtered by the WAF. It is a reminder for WAF vendors to include robust normalization and decoding techniques in their security frameworks.
Original tweet: https://twitter.com/codewithimanshu/status/1999913215044788649