CVE-2026-33018

libsixel is a SIXEL encoder/decoder implementation derived from kmiya's sixel. Versions 1.8.7 and prior contain a Use-After-Free vulnerability via the load_gif() function in fromgif.c, where a single sixel_frame_t object is reused across all frames of an animated GIF and gif_init_frame() unconditionally frees and reallocates frame->pixels between frames without consulting the object's reference count. Because the public API explicitly provides sixel_frame_ref() to retain a frame and sixel_frame_get_pixels() to access the raw pixel buffer, a callback following this documented usage pattern will hold a dangling pointer after the second frame is decoded, resulting in a heap use-after-free confirmed by ASAN. Any application using sixel_helper_load_image_file() with a multi-frame callback to process user-supplied animated GIFs is affected, with a reliable crash as the minimum impact and potential for code execution. This issue has been fixed in version 1.8.7-r1.

CVSS v3 7.0 HIGH

7.0^/10

CVSS v3 : HIGH

Vector :

Exploitability : 1.0 / Impact : 5.9

Attack Vector LOCAL

Attack Complexity HIGH

Privileges Required NONE

User Interaction REQUIRED

Confidentiality Impact HIGH

Integrity Impact HIGH

Availability Impact HIGH

Scope UNCHANGED

References

Link	Resource
https://github.com/saitoha/libsixel/releases/tag/v1.8.7-r1	Release Notes
https://github.com/saitoha/libsixel/security/advisories/GHSA-w46f-jr9f-rgvp	Exploit Vendor Advisory

Configurations

Configuration 1 (hide)

cpe:2.3:a:saitoha:libsixel:*:*:*:*:*:*:*:*

History

No history.

Information

Published : 2026-04-14 22:16

Updated : 2026-07-25 10:10

NVD link : CVE-2026-33018

Mitre link : CVE-2026-33018

CVE.ORG link : CVE-2026-33018

JSON object : View

Products Affected

saitoha

libsixel

CWE

CWE-416

Use After Free

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