CVE-2026-43907: OpenImageIO: Integer overflow in QueryRGBBufferSizeInternal leads to heap out-of-bounds write in DPX decoder (kCbYCr and kABGR)

OpenImageIO is a toolset for reading, writing, and manipulating image files of any image file format relevant to VFX / animation. Prior to 3.0.18.0 and 3.1.13.0, a signed integer overflow in QueryRGBBufferSizeInternal() in DPXColorConverter.cpp leads to a heap-based out-of-bounds write when processing crafted DPX image files. The function computes buffer sizes using 32-bit signed integer arithmetic with negative multipliers (e.g., pixels * -3 * bytes for kCbYCr descriptors and pixels * -4 * bytes for kABGR descriptors), where a negative result is used as an in-band signal that no separate buffer is needed. When the pixel count is sufficiently large, the multiplication overflows INT_MIN and wraps to a small positive value. The caller in dpxinput.cpp interprets this positive value as a required buffer size, allocates an undersized heap buffer via m_decodebuf.resize(), and then writes the full image data into it via fread, resulting in a heap buffer overflow. An attacker can exploit this by crafting a DPX file that triggers the overflow, causing a denial of service (crash) or potentially arbitrary code execution through heap corruption in any application that reads pixel data using OpenImageIO. This vulnerability is fixed in 3.0.18.0 and 3.1.13.0.