A vulnerability has been discovered and corrected in Mozilla NSS: The ssl_Do1stHandshake function in sslsecur.c in libssl in Mozilla Network Security Services before 3.15.4, when the TLS False Start feature is enabled, allows man-in-the-middle attackers to spoof SSL servers by using an arbitrary X.509 certificate during certain handshake traffic . The updated packages have been upgraded to the 3.15.4 version which is not vulnerable to this issue.