This tweet mentions a bypass related to the Log4Shell vulnerability, which is a Remote Code Execution (RCE) vulnerability. The bypass technique involves very complex obfuscation used in an attack sample captured through a honeypot. The obfuscation is used to counteract Web Application Firewalls (WAFs) that rely on regular expressions for detection. These regex-based detection methods can be evaded by attackers who craft obfuscated payloads, making it difficult for the WAF to recognize malicious patterns. The tweet credits @SimoKohonen for sharing the attack sample and suggests that the author has an implementation that can handle or detect such obfuscated attacks. The exact WAF vendor is not specified in the tweet. This example highlights the challenge of protecting applications with regex-based WAFs against sophisticated, obfuscated exploit payloads targeting vulnerabilities like Log4Shell.
For more details, check out the original tweet here: https://twitter.com/pyn3rd/status/1999453264618910092