Vulnerability in saitoha libsixel

[ Why it matters ]Priority signals

• Public proof-of-concept exploit exists (CISA SSVC)

[ Description ]Official description

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.

[ Fixes ]Fixes and patches

No fix or interim patch is linked from our sources yet. Check the vendor references below and limit exposure of affected systems until a fix is available.

[ References ]References

• github.com/libsixel/libsixel/blob/v1.10.5/src/fromgif.c
• github.com/saitoha/libsixel/blob/v1.8.7/src/fromgif.c
• github.com/saitoha/libsixel/commit/bdbab09816eb9188429c37a50b97c5e66dfe5047
• github.com/saitoha/libsixel/issues/220
• github.com/saitoha/libsixel/releases/tag/v1.8.7-r1
• hackmd.io/@haind-pwn/libsixel-gif-transparent-index-oob-write
• www.vulncheck.com/advisories/libsixel-before-1.8.7-r1-and-1.9.0-through-1.10.5-heap-out…