On May 20, 2015, researchers from the University of Michigan announced a new vulnerability in the Diffie-Hellman key exchange, called LogJam.

The vulnerability resides in the basic design of TLS itself, exposing both clients and servers, including mail servers, to a MitM attack, in which a malicious attacker can downgrade SSL-based connections to 512-bit export-grade cryptography, thus bypassing the basic security mechanism and allowing the attacker to read and modify any exposed traffic. 419 more words