Some time ago I reported a bug to Apple found by fuzzing PDFs.

The bug resides inside the CoreGraphics code, and it’s related to JPEGs.

You can find the reproducer PDF here. To trigger it you need to code yourself some code that interacts with CoreGraphics.

Apple Advisory:

CoreGraphics Available for: iPhone 5 and later, iPad 4th generation and later, iPod touch 6th generation and later Impact: Viewing a maliciously crafted JPEG file may lead to arbitrary code execution Description: A memory corruption issue was addressed through improved memory handling.