{"id":"CVE-2026-33023","summary":"libsixel: Use-after-free in load_with_gdkpixbuf()","details":"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 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.","aliases":["GHSA-hr25-g2j6-qjw6"],"modified":"2026-07-08T08:12:26.905485872Z","published":"2026-04-14T22:05:31.493Z","database_specific":{"cwe_ids":["CWE-416"],"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/33xxx/CVE-2026-33023.json","cna_assigner":"GitHub_M"},"references":[{"type":"WEB","url":"https://github.com/saitoha/libsixel/releases/tag/v1.8.7-r1"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/33xxx/CVE-2026-33023.json"},{"type":"ADVISORY","url":"https://github.com/saitoha/libsixel/security/advisories/GHSA-hr25-g2j6-qjw6"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-33023"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/saitoha/libsixel","events":[{"introduced":"0"},{"fixed":"6d628cf43548e1f2739cbb13afcc6e8257868db5"}],"database_specific":{"cpe":"cpe:2.3:a:saitoha:libsixel:*:*:*:*:*:*:*:*","source":["CPE_RANGE","REFERENCES"],"extracted_events":[{"introduced":"0"},{"last_affected":"1.8.7"}]}}],"versions":["v1.8.7","nightly-latest","v1.8.6","v1.8.5","v1.8.4","v1.8.3","v1.8.2","v1.8.1","v1.8.0","v1.7.3","v1.7.2","v1.7.1","v1.6.1","v1.5.2","v1.5.1","v1.5.0","v1.4.13","v1.4.12","v1.4.11","v1.4.10","v1.4.9","v1.4.8","v1.4.7","v1.4.6","v1.4.5","v1.4.4","v1.4.3","v1.4.2","v1.4.1","v1.4.0","v1.3.6","v1.3.5","v1.3.4","v1.3.3","v1.3.2","v1.3.1","v1.1.2","v1.1.1","v1.1.0","v1.0.2","v1.0.1","v1.0.0","v0.28.0","v0.27.1","v0.27.0","v0.26.0","v0.25.5","v0.25.4","v0.25.3","v0.25.2","v0.25.1","v0.25.0","v0.24.2","v0.24.0","v0.23.2","v0.23.1","v0.23.0","v0.22.3","v0.22.2","v0.22.1","v0.22.0","v0.21.1","v0.21.0","v0.20.0","v0.19.6","v0.19.5","v0.19.4","v0.19.3","v0.19.2","v0.18.0","v0.17.2","v0.17.1","v0.17.0","v0.16.1","v0.16.0","v0.15.0","v0.14.0"],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-33023.json"}}],"schema_version":"1.7.5","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H"}]}