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7.3
Outdated libsixel versions crash or may execute malicious code
CVE-2026-33021
Summary
A bug in older versions of libsixel can cause a program to crash or run malicious code if it processes certain image files. This issue affects versions prior to 1.8.7-r1. To fix this, update to the latest version of libsixel.
Original title
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_in...
Original 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.
nvd CVSS3.1
7.3
Vulnerability type
CWE-416
Use After Free
Published: 14 Apr 2026 · Updated: 15 Apr 2026 · First seen: 15 Apr 2026