RHSA-2015:1185 — Security Advisory

Updated nss and nss-util packages that fix one security issue, several bugs and add various enhancements are now available for Red Hat Enterprise Linux 6 and 7.

Red Hat Product Security has rated this update as having Moderate security impact. Common Vulnerability Scoring System (CVSS) base scores, which give detailed severity ratings, are available for each vulnerability from the CVE links in the References section.

Network Security Services (NSS) 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 (DH) 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. (CVE-2015-4000)

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.

The nss and nss-util packages have been upgraded to upstream versions 3.19.1. The upgraded versions provide a number of bug fixes and enhancements over the previous versions.

Users of nss and nss-util are advised to upgrade to these updated packages, which fix these security flaws, bugs, and add these enhancements.