{"id":"CVE-2026-33023","title":"libsixel is a SIXEL encoder/decoder implementation derived from kmiya's sixel","summary":"libsixel is a SIXEL encoder/decoder implementation derived from kmiya's sixel. In versions 1.8.7 and prior, when built with the --with-gdk-pixbuf2 option, a use-after-free vulnerability exists in load_with_gdkpixbuf() in loader.c. The cl…","severity":"high","cvss":7.8,"cvssVector":"CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H","cwe":["CWE-416"],"vendor":"saitoha","product":"libsixel","affected":["libsixel <= 1.8.7"],"published":"2026-04-14","updated":"2026-07-25","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-33023","references":[{"url":"https://github.com/saitoha/libsixel/releases/tag/v1.8.7-r1","label":"security-advisories@github.com"},{"url":"https://github.com/saitoha/libsixel/security/advisories/GHSA-hr25-g2j6-qjw6","label":"security-advisories@github.com"},{"url":"https://github.com/saitoha/libsixel/security/advisories/GHSA-hr25-g2j6-qjw6","label":"134c704f-9b21-4f2e-91b3-4a467353bcc0"}],"tags":["nvd"],"epss":0.00289,"epssPercentile":0.21754,"ingestedAt":"2026-07-26T10:11:59.908Z","slug":"CVE-2026-33023","body":"## Overview\n\nlibsixel is a SIXEL encoder/decoder implementation derived from kmiya's sixel. In versions 1.8.7 and prior, when built with the --with-gdk-pixbuf2 option, a use-after-free vulnerability exists in load_with_gdkpixbuf() in loader.c. The cleanup path manually frees the sixel_frame_t object and its internal buffers without consulting the reference count, even though the object was created via the refcounted constructor sixel_frame_new() and exposed to the public callback. A callback that calls sixel_frame_ref(frame) to retain a logically valid reference will hold a dangling pointer after sixel_helper_load_image_file() returns, and any subsequent access to the frame or its fields triggers a use-after-free confirmed by AddressSanitizer. The root cause is a consistency failure between two cleanup strategies in the same codebase: sixel_frame_unref() is used in load_with_builtin() but raw free() is used in load_with_gdkpixbuf(). An attacker supplying a crafted image to any application built against libsixel with gdk-pixbuf2 support can trigger this reliably, potentially leading to information disclosure, memory corruption, or code execution. This issue has been fixed in version 1.8.7-r1.\n\n## Affected\n\n- `libsixel <= 1.8.7`\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"twilight","depthScore":43,"depthScoreParts":{"impact":42.9,"likelihood":0.1,"exploitation":0,"ransomware":0},"changes":[]}