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TI-2026-25467 Aliases CVE-2026-33021

libsixel: Use-after-free in sixel_encoder_encode_bytes()

Priority HIGH 65CWE-416Published · Updated

Key facts

Attack vector
Local
Privileges required
None
User interaction
None
Attack complexity
Low
Impact type
—
Confidentiality · integrity · availability
Low · Low · High
Fix status
Fixed

Attack profile from CVSS 3.1 · CNA. Fix status from CNA.

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 in sixel_encoder_encode_bytes() because sixel_frame_init() stores the caller-owned pixel buffer pointer directly in frame->pixels without making a defensive copy. When a resize operation is triggered, sixel_frame_convert_to_rgb888() unconditionally frees this caller-owned buffer and replaces it with a new internal allocation, leaving the caller with a dangling pointer. Any subsequent access to the original buffer by the caller constitutes a use-after-free, confirmed by AddressSanitizer. An attacker who controls incoming frames can trigger this bug repeatedly and predictably, resulting in a reliable crash with 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 0.00247 16th percentileScored 2026-11-07
Public exploit Yes 1 exploit referenceTagged by NVD
Fix Fixed libsixel (saitoha): 1.8.7-r1

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
Poc
Automatable
No
Technical impact
Partial

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-r11.8.7-r1Patch availableCNA
  • libsixel Vendorsaitoha Affected before 1.8.7-r1 Fixed in 1.8.7-r1 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-r1

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-2026-33021

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-2026-25464 libsixel: Use-After-Free in load_gif() CVSS 3.1HIGH 7.0
  • 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