Via Slashdot, I just ran across Didier Stevens post on how to automate the JBIG2decode vulnerability in PDF documents. There is a video on the site where he runs through three scenarios to exercise the vulnerability – Manually starting up Reader, viewing a thumbnail PDF, and then automatic execution by simply visiting the page with the malicious document through Windows Explorer Shell Extensions, and shows you the results in the debugger. It’s worth the view.
When you install Adobe Acrobat Reader, a Column Handler Shell Extension is installed. A column handler is a special program (a COM object) that will provide Windows Explorer with additional data to display (in extra columns) for the file types the column handler supports. The PDF column handler adds a few extra columns, like the Title. When a PDF document is listed in a Windows Explorer windows, the PDF column handler shell extension will be called by Windows Explorer when it needs the additional column info. The PDF column handler will read the PDF document to extract the necessary info, like the Title, Author.
I also ran across another technical analysis here. As you don’t need to do anything other that drop onto an infected site, this is a pretty serious issue. There is supposed to be a patch available later this month. The more I look at this, the more I think it may be a good idea to disable Reader until there is a patch. There are some instructions on how to do this on the PC Mag site, and some additional information you might find helpful as well.