According to the CVSS metric, user interaction is required (UI:R). What interaction would the user have to do? In a web-based attack scenario, an attacker could host a website (or leverage a compromised website that accepts or hosts user-provided content) that contains a specially crafted file that is designed to exploit the vulnerability. However, an attacker would have no way to force the user to visit the website. Instead, an attacker would have to convince the user to click a link, typically by way of an enticement in an email or Instant Messenger message, and then convince the user to open the specially crafted file.
Steven Seeley (mr_me) of Source Incite working with Trend Micro Zero Day Initiative