What is a vulnerability of an unauthenticated Dime-Heliman exchange?

The vulnerability of an unauthenticated Diffie-Hellman exchange, particularly when it comes to the risk of a man-in-the-middle (MITM) attack, is a significant concern. In this scenario, a hacker can intercept the public values exchanged between two legitimate parties and substitute them with their own. This allows the attacker to decrypt or manipulate the messages passing between the two original parties without them knowing. This answer is based on the fundamental principles of how Diffie-Hellman key exchange works and its vulnerabilities without authentication mechanisms. Reference materials from cryptographic textbooks and security protocols detail these vulnerabilities, such as those found in standards and publications by organizations like NIST.