This post discusses an approach to bypassing Web Application Firewalls (WAFs) by exploiting context-aware injection vulnerabilities in multipart file upload endpoints. Many WAFs fail to properly inspect injections in the boundaries of multipart file uploads, especially when attackers upload special files like .htaccess to manipulate server behavior or use eval constructs to execute arbitrary code. The tweet suggests focusing on such injection points to find bypass patterns. The technique involves uploading files with malicious content in multipart boundaries that evade conventional WAF detection mechanisms, allowing attackers to execute server-side code or alter access controls. This highlights the importance of thorough validation and filtering on file upload endpoints and comprehensive inspection of multipart request boundaries by WAFs to prevent such bypasses.
Original tweet: https://twitter.com/tech_maddy/status/1998071795375833556