CVE-2026-33023 libsixel: Use-after-free in load_with_gdkpixbuf()

libsixel is a SIXEL encoder/decoder implementation derived from kmiya's sixel. In versions 1.8.7 and prior, when built with the --with-gdk-pixbuf2 option, a use-after-free vulnerability exists in loadwithgdkpixbuf in loader.c. The cleanup path manually frees the sixelframet object and its interna...