Created php tracking bugs for this issue:

Affects: fedora-all [bug 1359837]

PHP prior to 5.4.0 does not have this class and is not affected.

Reliable remote exploitation most likely requires the use of input unserialization. Doing so it documented as being unsafe:

  http://php.net/manual/en/function.unserialize.php

  Do not pass untrusted user input to unserialize(). Unserialization can
  result in code being loaded and executed due to object instantiation and
  autoloading, and a malicious user may be able to exploit this. Use a safe,
  standard data interchange format such as JSON (via json_decode() and
  json_encode()) if you need to pass serialized data to the user.

There may be other methods, but those are probably not very suitable to exploit this remotely in a realistic scenario.

This issue has been addressed in the following products:

  Red Hat Software Collections for Red Hat Enterprise Linux 6
  Red Hat Software Collections for Red Hat Enterprise Linux 6.7 EUS
  Red Hat Software Collections for Red Hat Enterprise Linux 7
  Red Hat Software Collections for Red Hat Enterprise Linux 7.2 EUS
  Red Hat Software Collections for Red Hat Enterprise Linux 7.3 EUS

Via RHSA-2016:2750 https://rhn.redhat.com/errata/RHSA-2016-2750.html