Read the docs
TI-2026-25464 Aliases CVE-2026-33018

libsixel: Use-After-Free in load_gif()

Priority HIGH 66CWE-416Published · Updated

Key facts

Attack vector
Local
Privileges required
None
User interaction
Required
Attack complexity
High
Impact type
Code execution
Confidentiality · integrity · availability
High · High · High
Fix status
Fixed

Attack profile from CVSS 3.1 · CNA. Fix status from CNA. Impact type from CWE-416 and the CVSS impact.

Summary

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.

Why it matters now

Exploitation Proof of concept CISA SSVC · not in CISA KEV
EPSS 0.00191 8th percentileScored 2026-11-07
Public exploit Yes 1 exploit referenceTagged by NVD
Fix Fixed libsixel (saitoha): 1.8.7-rc1

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
Poc
Automatable
No
Technical impact
Total

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
saitohalibsixelbefore 1.8.7-rc11.8.7-rc1Patch availableCNA
  • libsixel Vendorsaitoha Affected before 1.8.7-rc1 Fixed in 1.8.7-rc1 Patch available CNA

CPE configurations NVD · 1

CPEVersionsRoleVendor
cpe:2.3:a:saitoha:libsixel:*:*:*:*:*:*:*:*before 1.8.7-r1Vulnerablesaitoha
  • cpe:2.3:a:saitoha:libsixel:*:*:*:*:*:*:*:* Versions before 1.8.7-r1 Vulnerable ·saitoha

Remediation

  • Fix · CNA libsixel (saitoha) Fixed in 1.8.7-rc1

Vendor assessments

Red Hat

Red Hat's page for this CVE →

Not affected: 1 product
  • Red Hat

Timeline

  1. 2026-10-02 Threatist record created from CVE-2026-33018

References

Exploit 1

Other 1

  • TI-2026-32536 libsixel: integer overflow in encoder CVSS 3.1HIGH 7.8
  • TI-2026-25469 libsixel: Use-after-free in load_with_gdkpixbuf() CVSS 3.1HIGH 7.8
  • TI-2026-32537 libsixel: integer overflow in parser CVSS 3.1HIGH 7.1
  • TI-2026-25466 libsixel: Integer Overflow in write_png_to_file() leads to Heap-based Buffer Overflow CVSS 3.1HIGH 7.1
  • TI-2026-25467 libsixel: Use-after-free in sixel_encoder_encode_bytes() CVSS 3.1HIGH 7.3
  • TI-2026-25465 libsixel: Integer overflow leads to Out-of-bounds Read in img2sixel CVSS 3.1HIGH 7.1
See all 47 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences