Imager::File::GIF versions before 1.006 for Perl allow out-of-bounds reads when consolidating GIF images

Imager::File::GIF versions before 1.006 for Perl allow out-of-bounds reads when consolidating GIF images.

With `gif_consolidate => 1`, palette indices from the image are used without checking the colour table's bounds. The i_readgif_low routine reads beyond the heap allocation and copies the bytes into output pixels. The default GIF reader is not affected.

The same code ships bundled in the Imager distribution.

An attacker supplying a crafted GIF can disclose adjacent heap memory through the decoded output and may crash the process.