PYSEC-2026-2846 OpenEXR's CompositeDeepScanLine integer-overflow leads to heap OOB write

Summary Function: CompositeDeepScanLine::readPixels, reachable from high-level multipart deep read flows MultiPartInputFile + DeepScanLineInputPart + CompositeDeepScanLine. Vulnerable lines src/lib/OpenEXR/ImfCompositeDeepScanLine.cpp: - totalsizesptr += countsjptr; line 511 - overallsamplecount ...