Red Hat Security Advisory 2015-1072-01 – OpenSSL is a toolkit that implements the Secure Sockets Layer and Transport Layer Security protocols, as well as a full-strength, general purpose cryptography library. A flaw was found in the way the TLS protocol composes the Diffie-Hellman key exchange. A man-in-the-middle attacker could use this flaw to force the use of weak 512 bit export-grade keys during the key exchange, allowing them do decrypt all traffic. Note: This update forces the TLS/SSL client implementation in OpenSSL to reject DH key sizes below 768 bits, which prevents sessions to be downgraded to export-grade keys. Future updates may raise this limit to 1024 bits.