H.D. Moore has released instructions on writing a critical exploit that leverages a bug in how Apple’s iPhone handles TIFF image files and, to enable the writing of exploits, has put out a new version of his Weasel debugger that can handle the peculiarities of the phone’s ARM processors. At this point, the exploit can only take over phones that have been tinkered with, but Moore is promising to post instructions on how to exploit unmodified iPhones soon.

The vulnerability in question is in libtiff, the iPhone’s library for reading and writing TIFF files. From the get-go, Apple shipped the iPhone with a vulnerable version of libtiff and didn’t bother to fix it in the recent 1.1.1 update–“fortunately for the iPhone development community,” Moore noted in an Oct. 11 posting that was the first of his two-part series on cracking the iPhone. The vulnerability can be exploited through the phone’s MobileSafari Web browser.