CVEvulnerability
CVE-2026-33021
7.3 HIGH
Official page ↗
- Status
- Analyzed
- Published
- 2026-04-14
- Last modified
- 2026-07-25
- Assigner
- [email protected]
- CVSS 3.1 ([email protected])
- 7.3 HIGH — CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:H
- Weaknesses
- CWE-416
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 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.
Affected configurations
• saitoha libsixel (< 1.8.7-r1)
Related
Weakness · CWE (1)
- CWE-416 Use After Free weakness
References
- https://github.com/saitoha/libsixel/releases/tag/v1.8.7-r1 Release Notes
- https://github.com/saitoha/libsixel/security/advisories/GHSA-j6m5-2cc7-3whc Exploit, Vendor Advisory