Imager versions before 1.037 for Perl overflow a heap buffer fetching float samples from a paletted image in i_gsampf_fp.
For a paletted image, getsamples() with type "float" allocates a buffer of one sample per pixel and fetches every requested channel of each pixel into it. Requesting more than one channel writes past its end.
An attacker-supplied image controls the overflowing bytes through its palette.
Upgrade to Imager 1.037 or later.