GIMP 2.10.6 out-of-range RGB values from .CR2 file

Some pixels in this RGB image have extremely saturated colors, outside the gamut that can be displayed on a video monitor whose primaries match Rec. ITU-R BT.709. All RGB triples in the image correspond to CIE xyY triples with xy chromaticities that represent real colors.

So convert to your reference space, and clip.