stable-diffusion.cpp: Heap buffer overflow in GLOBAL opcode parsing for PyTorch checkpoint files

Summary

stable-diffusion.cpp is a pure C/C++ library for running diffusion model (Stable Diffusion, Flux, Wan, Qwen Image, Z-Image, and more) inference. In versions prior to master-584-0a7ae07, the pickle .ckpt parser in src/model.cpp contained a heap buffer overflow vulnerability in the GLOBAL opcode handler. The issue was caused by missing validation when searching for newline-delimited fields. A crafted .ckpt file without the expected newline could cause the parser to use -1 as a copy length, resulting in immediate heap corruption. The attack requires the victim or application to load a .ckpt file from an untrusted source, such as a downloaded model from a model sharing site. The issue has been resolved in version master-584-0a7ae07. If developers are unable to immediately update their applications they can work around this issue by following these instructions: do not load .ckpt checkpoint files from untrusted sources, and prefer trusted model sources and safer formats such as .safetensors where possible.