REVERSE ENGINEERING OF APPLE'S IOS 0-CLICK CVE-2025-43300: 2 BYTES THAT MAKE SIZE MATTER

Summary from the TLDR InfoSec newsletter

CVE-2025-43300 is a zero-click out-of-bounds write vulnerability in the ImageIO framework that occurs when processing DNG images with JPEG lossless compression. Exploited in the wild, the vulnerability stems from incorrect buffer allocation and loop bounds in the lossless JPEG decompression code, where the system assumes at least two components per pixel but processes images with only 1 component, causing writes beyond allocated memory. Apple's patch adds bounds checking to verify buffer size before each write operation and raises an exception when the buffer would be exceeded, fixing the mismatch between allocated buffer size (based on components per pixel) and actual write operations.