CVE-2026-110601

libsixel before 1.8.7-r1 and 1.9.0 through 1.10.5 contains a heap out-of-bounds write vulnerability in gif_init_frame() in src/fromgif.c, which never checks the GIF transparent color index against the palette size. Attackers can supply a crafted GIF with a small color table and large transparent index, processed with a background color set, to write bytes past the palette buffer, causing heap corruption or crashes.

• https://github.com/libsixel/libsixel/blob/v1.10.5/src/fromgif.c#L219-L240
• https://github.com/saitoha/libsixel/blob/v1.8.7/src/fromgif.c#L182-L248
• https://github.com/saitoha/libsixel/commit/bdbab09816eb9188429c37a50b97c5e66dfe5047
• https://github.com/saitoha/libsixel/issues/220
• https://github.com/saitoha/libsixel/releases/tag/v1.8.7-r1
• https://hackmd.io/@haind-pwn/libsixel-gif-transparent-index-oob-write
• https://www.vulncheck.com/advisories/libsixel-before-1.8.7-r1-and-1.9.0-through-1.10.5-heap-out-of-bounds-write-via-gif
• https://github.com/saitoha/libsixel/issues/220