OpenEXR provides the specification and reference implementation of the EXR file format, an image storage format for the motion picture industry. In CompositeDeepScanLine::readPixels, per-pixel totals are accumulated in vector<unsigned int> total_sizes for attacker-controlled large counts across many parts, total_sizes[ptr] wraps modulo 2^32. overall_sample_count is then derived from wrapped totals and used in samples[channel].resize(overall_sample_count). Decode pointer setup/consumption proceeds with true sample counts, and write operations in core unpack (generic_unpack_deep_pointers) overrun the undersized composite sample buffer.

This vulnerability is fixed in v3.2.6, v3.3.8, and v3.4.6.