gdImageGd2Ptr in gd_gd2.c in the GD Graphics Library (aka LibGD) through 2.3.2 has a double free. NOTE: the vendor's position is "The GD2 image format is a proprietary image format of libgd. It has to be regarded as being obsolete, and should only be used for development and testing purposes.
https://github.com/libgd/libgd/pull/713
https://github.com/libgd/libgd/issues/700
https://github.com/libgd/libgd/commit/c5fd25ce0e48fd5618a972ca9f5e28d6d62006af