Red Hat Security Advisory 2015-1185-01 – Network Security Services is a set of libraries designed to support cross-platform development of security-enabled client and server applications. 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 NSS 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.