Exploiting a heap buffer overflow in linux

In the previous article, we dissected glibc's malloc — chunks, bins, tcache, coalescing, and the metadata that holds it all together. Now we break it.

Heap exploitation is fundamentally different from stack exploitation. On the stack, the goal is clear: overwrite the return address, control EIP. On the heap, there's no return address to overwrite. Instead, we corrupt the allocator's metadata to trick malloc() into returning a pointer to memory we want to control — a function pointer, a GOT entry, a vtable, or any other target.