And just like the last time this happened, you have to jailbreak the phone in order to install the patch. That said, this vulnerability is caused by PDF files... and PDF files have been a pain in the ass for multiple platforms for ages.
I may be wrong, but I believe Apple writes their own PDF reading software, rather than use that as supplied by Adobe. That could be an issue with why these types of exploits tend to happen more often on the Apple PDF reader - it's not as tracked as the Adobe official offering.