libpng: Heap buffer overflow in `png_set_quantize`

Classification: Severe, Solution: Official Fix, Exploit Maturity: Unproven, CVSSv3.1: 8.3, CVEs: CVE-2026-25646, Summary: An out-of-bounds read vulnerability exists in the png_set_quantize() API function. When the function is called with no histogram and the number of colors in the palette is more than twice the maximum supported by the user's display, certain palettes will cause the function to enter into an infinite loop that reads past the end of an internal heap-allocated buffer. The images