libpng buffer overflow in png_set_PLTE

libpng reports:

CVE for a vulnerability in libpng, all versions, in the
png_set_PLTE/png_get_PLTE functions. These functions failed to check for
an out-of-range palette when reading or writing PNG files with a bit_depth
less than 8. Some applications might read the bit depth from the IHDR
chunk and allocate memory for a 2^N entry palette, while libpng can return
a palette with up to 256 entries even when the bit depth is less than 8.