mono - security update

Three issues with Mono’s TLS stack are addressed.

• CVE-2015-2318
  Mono’s implementation of the SSL/TLS stack failed to check
  the order of the handshake messages. Which would allow
  various attacks on the protocol to succeed. (“SKIP-TLS”)
• CVE-2015-2319
  Mono’s implementation of SSL/TLS also contained support for
  the weak EXPORT cyphers and was susceptible to the FREAK attack.
• CVE-2015-2320
  Mono contained SSLv2 fallback code, which is no longer needed
  and can be considered insecure.

For Debian 6 Squeeze, these issues have been fixed in mono version 2.6.7-5.1+deb6u1