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CVE-2026-33018

Saitoha Libsixel use-after-free

7.0 HIGHPublic exploitEPSS 0.19%
  1. Published14 Apr 2026

Description

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 3.1 breakdown

Attack vectorLocal
Attack complexityHigh
Privileges requiredNone
User interactionRequired
ScopeUnchanged
ConfidentialityHigh
IntegrityHigh
AvailabilityHigh
CVSS:3.1/AV:L/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H

Affected products

Saitoha Libsixel< 1.8.7-r1

Remediation

Fixed in
Saitoha Libsixel≥ 1.8.7-r1

References

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Frequently asked

Is CVE-2026-33018 being actively exploited?

CVE-2026-33018 is not in the CISA KEV catalog. A public exploit reference exists, so treat it as exploitable. Its EPSS exploit probability is 0.19%.

How severe is CVE-2026-33018?

CVE-2026-33018 has a CVSS 3.1 base score of 7.0, rated high. EPSS estimates a 0.19% probability of exploitation.

Which products are affected by CVE-2026-33018?

Affected products include Saitoha Libsixel.

How do I fix CVE-2026-33018?

Upgrade affected software to a fixed version, for example Saitoha Libsixel 1.8.7-r1 or later, then confirm no affected versions remain in your inventory.

How Secuno handles this

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Data from the NVD, CISA KEV catalog and FIRST EPSS. CVSS 3.1 base score shown where available.