Race condition in libssl in Mozilla Network Security Services (NSS) before 3.15.4, as used in Mozilla Firefox before 27.0, Firefox ESR 24.x before 24.3, Thunderbird before 24.3, SeaMonkey before 2.24, and other products, allows remote attackers to cause a denial of service (use-after-free) or possibly have unspecified other impact via vectors involving a resumption handshake that triggers incorrect replacement of a session ticket.