The other reason is Acrobat is often outdated. I can't fathom the number of times I've been looking over someone's shoulder who opened a PDF and ignored the warning that updates are ready to download and install. It's incredibly frustrating because many of them know better. They understand the importance of keeping their AV updated and Windows patched, but they've never made the connection that apps like Acrobat and Firefox should be updated, too.
What's the impact? It depends on which side of the fence you're on. For defenders, it's time to make sure you have rules in your IDS or IPS to try and pick up malicious PDF files. Follow the mitigations in the US-CERT Vulnerability Note VU#666281. Make sure your users are aware of the current issues with PDFs, and keep them updated on when patches are applied to fix the problem. You might even consider an alternative PDF application, but beware because they might have a similar vulnerability, as we saw with Foxit Reader.
Pen testers are going to enjoy this vulnerability for what I think will be quite a while, and there's so many ways to take advantage of it. You could create a malicious PDF embedded with a Metasploit Framework payload that phones home, allowing remote control. That PDF could then be sent via e-mail to your victim. If attachments are disallowed, you could post it to a Website, e-mail, IM, or even tweet a link to it. Or you could walk into an office and ask the secretary to print the document for you and hand her a thumb drive as I believe Chris Nickerson did in an episode of Tiger Team (Listen to an interview with Chris on Security Justice podcast for more info).
Whatever side you're on, there's work to be done.
John H. Sawyer is a senior security engineer on the IT Security Team at the University of Florida. The views and opinions expressed in this blog are his own and do not represent the views and opinions of the UF IT Security Team or the University of Florida. When John's not fighting flaming, malware-infested machines or performing autopsies on blitzed boxes, he can usually be found hanging with his family, bouncing a baby on one knee and balancing a laptop on the other. Special to Dark Reading.