LIBPNG is vulnerable to a heap buffer overflow in `png_do_quantize` via malformed palette index

Vulnerability Description

LIBPNG is a reference library for use in applications that read, create, and manipulate PNG (Portable Network Graphics) raster image files. Prior to version 1.6.51, a heap buffer over-read vulnerability exists in libpng's png_do_quantize function when processing PNG files with malformed palette indices. The vulnerability occurs when palette_lookup array bounds are not validated against externally-supplied image data, allowing an attacker to craft a PNG file with out-of-range palette indices that trigger out-of-bounds memory access. This issue has been patched in version 1.6.51.

References

• https://github.com/pnggroup/libpng/security/advisories/GHSA-4952-h5wq-4m42
• https://github.com/pnggroup/libpng/pull/748
• https://github.com/pnggroup/libpng/commit/6a528eb5fd0dd7f6de1c39d30de0e41473431c37