This tweet discusses a bypass method for Web Application Firewalls (WAF) specifically targeting the Log4Shell vulnerability, which is a Remote Code Execution (RCE) type vulnerability. Thanks to @SimoKohonen for sharing an attack sample captured via a honeypot. The highlight here is the use of very complex obfuscation in the attack payload, which is a common technique used to defeat WAF detection that rely on regular expression based filtering. The implementation mentioned in the tweet is capable of restoring or decoding this complex obfuscation, making it possible to analyze the true payload. This indicates that attackers are employing advanced obfuscation methods to evade WAFs, and defensive tools need to evolve to detect such sophisticated evasion techniques effectively.
For more insights, check out the original tweet here: https://twitter.com/pyn3rd/status/1999439370609393908