SPLITTING THE EMAIL ATOM: EXPLOITING PARSERS TO BYPASS ACCESS CONTROLS

Summary from the TLDR InfoSec newsletter

This article details an exploration of how email parsers handle the more arcane parts of the RFC. It begins with background about ways that the RFC treats some special characters like escapes and comments. The article then details how the author utilized encoded words to bypass access controls to obtain access to protected environments using encoded words before taking it a step further to achieve RCE using puny codes. Relevant tooling for automating encoded word discovery with Turbo Intruder and fuzzing with punycode as well as a CTF are included.