Millions of networks are relying on Windows authentication protocols to secure their logins, and consequently, their network's integrity. In this talk, we will show a surprising chosen-plaintext attack exploiting a logical vulnerability in one of Windows' more common protocols. The vulnerability affects a wide array of applications including Microsoft Remote Desktop. The attack enables remote code execution and, while being mathematically and technically complex, is very easy to utilize and has nearly 100% of success. The talk will include a live demonstration of the attack along with a rich description of the technical vulnerability details.