CVE-2026-43909: OpenImageIO: Signed integer overflow in SwapRGBABytes loop index leads to out-of-bounds read/write in DPX ABGR decoder

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 32-bit integer overflow in the loop index expression i * 4 inside SwapRGBABytes() causes the function to compute a large negative pointer offset when processing kABGR DPX images with large dimensions. The immediate crash is an out-of-bounds read (the memcpy at line 45 reads from &input[i * 4] first), but the subsequent write operations at lines 46–49 target the same wrapped offset — making this a combined OOB read+write primitive. This vulnerability is fixed in 3.0.18.0 and 3.1.13.0.