CVE-2015-2721

Name of the Vulnerable Software and Affected Versions Mozilla Network Security Services (NSS) versions prior to 3.19 Mozilla Firefox versions prior to 39.0 Firefox ESR versions 31.x prior to 31.8 Firefox ESR versions 38.x prior to 38.1 Thunderbird versions prior to 38.1

Description The issue is related to the TLS state machine, where state transitions are not properly determined, allowing man-in-the-middle attackers to defeat cryptographic protection mechanisms by blocking messages. This can be demonstrated by removing a forward-secrecy property by blocking a ServerKeyExchange message, also known as a "SMACK SKIP-TLS" issue.

Recommendations For Mozilla Network Security Services (NSS) versions prior to 3.19, update to version 3.19 or later. For Mozilla Firefox versions prior to 39.0, update to version 39.0 or later. For Firefox ESR versions 31.x prior to 31.8, update to version 31.8 or later. For Firefox ESR versions 38.x prior to 38.1, update to version 38.1 or later. For Thunderbird versions prior to 38.1, update to version 38.1 or later.