The libTiff Exploit is an exploit that can be used to jailbreak iPhone OS 1.0-1.1.1. It is patched as of 1.1.2.
There was a buffer overflow in the iPhone's libtiff. This was exploited to run a small application to jailbreak and patch libtiff. This exploit was also used for PSP homebrew, which cmw also worked on. The source code of the exploit was later released by cmw on his blog.