CVE-2015-2721: Canonical Ubuntu Linux

Medium severity, CVSS 4.3. EPSS: 3.3% chance of exploitation in the next 30 days.

Mozilla Network Security Services (NSS) before 3.19, as used in Mozilla Firefox before 39.0, Firefox ESR 31.x before 31.8 and 38.x before 38.1, Thunderbird before 38.1, and other products, does not properly determine state transitions for the TLS state machine, which allows man-in-the-middle attackers to defeat cryptographic protection mechanisms by blocking messages, as demonstrated by removing a forward-secrecy property by blocking a ServerKeyExchange message, aka a "SMACK SKIP-TLS" issue.

Affected products

• Canonical Ubuntu Linux: version 12.04 only; version 14.04 only; version 14.10 only; version 15.04 only
• Debian Debian Linux: version 7.0 only; version 8.0 only
• Mozilla Network Security Services: version 3.19 only
• Novell Suse Linux Enterprise Desktop: version 12.0 only
• Novell Suse Linux Enterprise Server: version 11 only; version 12.0 only
• Novell Suse Linux Enterprise Software Development Kit: version 12.0 only
• Oracle Solaris: version 11.3 only
• Oracle Vm Server: version 3.2 only

Published 2015-07-06. Last modified 2026-06-17.