PT-2026-32925 · Libsixel · Libsixel

Nicoppida · Published 2026-04-14 · Updated 2026-04-15 · CVE-2026-33018

Positive Technologies (AI Summary)

CVSS v3.1

7.0

High

Base vector

AV:L/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H

Name of the Vulnerable Software and Affected Versions libsixel versions prior to 1.8.7-r1

Description A Use-After-Free issue exists in the load gif() function within fromgif.c. This occurs because a single sixel frame t object is reused across all frames of an animated GIF, and the gif init frame() function frees and reallocates frame->pixels between frames without checking the object's reference count. Applications using sixel helper load image file() with a multi-frame callback to process user-supplied animated GIFs are affected. This can lead to a heap use-after-free when a callback uses sixel frame ref() to retain a frame and sixel frame get pixels() to access the raw pixel buffer, resulting in a dangling pointer after the second frame is decoded. This may cause a crash or potential code execution.

Recommendations Update to version 1.8.7-r1.

Fix

Use After Free

Weakness Enumeration

CWE-416

Related Identifiers

CVE-2026-33018

Affected Products

Libsixel

References · 10

• https://github.com/saitoha/libsixel/security/advisories/GHSA-w46f-jr9f-rgvp · Vendor Advisory
• https://osv.dev/vulnerability/UBUNTU-CVE-2026-33018 · Vendor Advisory
• https://osv.dev/vulnerability/DEBIAN-CVE-2026-33018 · Vendor Advisory
• https://ubuntu.com/security/CVE-2026-33018 · Vendor Advisory
• https://cve.org/CVERecord?id=CVE-2026-33018 · Security Note
• https://security-tracker.debian.org/tracker/CVE-2026-33018 · Vendor Advisory
• https://nvd.nist.gov/vuln/detail/CVE-2026-33018 · Security Note
• https://github.com/saitoha/libsixel/releases/tag/v1.8.7-r1 · Note
• https://twitter.com/VulmonFeeds/status/2044323457811239067 · Twitter Post
• https://twitter.com/CVEnew/status/2044338912915829001 · Twitter Post