Ubuntu: (Multiple Advisories) (CVE-2017-7508): OpenVPN vulnerabilities

Karthikeyan Bhargavan and Gaëtan Leurent discovered that 64-bit block
ciphers are vulnerable to a birthday attack. A remote attacker could
possibly use this issue to recover cleartext data. Fixing this issue
requires a configuration change to switch to a different cipher. This
update adds a warning to the log file when a 64-bit block cipher is in use.
This issue only affected Ubuntu 14.04 LTS, Ubuntu 16.04 LTS and
Ubuntu 16.10. (CVE-2016-6329)

It was discovered that OpenVPN incorrectly handled rollover of packet ids.
An authenticated remote attacker could use this issue to cause OpenVPN to
crash, resulting in a denial of service. This issue only affected Ubuntu
14.04 LTS, Ubuntu 16.04 LTS and Ubuntu 16.10. (CVE-2017-7479)

Guido Vranken discovered that OpenVPN incorrectly handled certain malformed
IPv6 packets. A remote attacker could use this issue to cause OpenVPN to
crash, resulting in a denial of service. (CVE-2017-7508)

Guido Vranken discovered that OpenVPN incorrectly handled an HTTP proxy
with NTLM authentication. A remote attacker could use this issue to cause
OpenVPN clients to crash, resulting in a denial of service, or possibly
expose sensitive memory contents. (CVE-2017-7520)

Guido Vranken discovered that OpenVPN incorrectly handled certain x509
extensions. A remote attacker could use this issue to cause OpenVPN to
crash, resulting in a denial of service. (CVE-2017-7521)