{"id":"DEBIAN-CVE-2026-33018","details":"libsixel is a SIXEL encoder/decoder implementation derived from kmiya's sixel. Versions 1.8.7 and prior contain a Use-After-Free vulnerability via the load_gif() function in fromgif.c, where a single sixel_frame_t object is reused across all frames of an animated GIF and gif_init_frame() unconditionally frees and reallocates frame-\u003epixels between frames without consulting the object's reference count. Because the public API explicitly provides sixel_frame_ref() to retain a frame and sixel_frame_get_pixels() to access the raw pixel buffer, a callback following this documented usage pattern will hold a dangling pointer after the second frame is decoded, resulting in a heap use-after-free confirmed by ASAN. Any application using sixel_helper_load_image_file() with a multi-frame callback to process user-supplied animated GIFs is affected, with a reliable crash as the minimum impact and potential for code execution. This issue has been fixed in version 1.8.7-r1.","modified":"2026-09-14T17:03:08.073946891Z","published":"2026-04-14T22:16:30.213Z","upstream":["CVE-2026-33018"],"references":[{"type":"ADVISORY","url":"https://security-tracker.debian.org/tracker/CVE-2026-33018"}],"affected":[{"package":{"name":"libsixel","ecosystem":"Debian:12","purl":"pkg:deb/debian/libsixel?arch=source&distro=bookworm"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1.10.3-3","1.10.5-1","1:1.8.7-1","1:1.8.7-2","1:1.8.7-3","1:1.8.7-4","1:1.8.7-5","1:1.8.7-6","1:1.8.7-r2-1"],"ecosystem_specific":{"urgency":"not yet assigned"},"database_specific":{"source":"https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2026-33018.json"}},{"package":{"name":"libsixel","ecosystem":"Debian:13","purl":"pkg:deb/debian/libsixel?arch=source&distro=trixie"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1.10.5-1","1:1.8.7-1","1:1.8.7-2","1:1.8.7-3","1:1.8.7-4","1:1.8.7-5","1:1.8.7-6","1:1.8.7-r2-1"],"ecosystem_specific":{"urgency":"not yet assigned"},"database_specific":{"source":"https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2026-33018.json"}},{"package":{"name":"libsixel","ecosystem":"Debian:14","purl":"pkg:deb/debian/libsixel?arch=source&distro=forky"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1:1.8.7-r2-1"}]}],"versions":["1.10.5-1","1:1.8.7-1","1:1.8.7-2","1:1.8.7-3","1:1.8.7-4","1:1.8.7-5","1:1.8.7-6"],"ecosystem_specific":{"urgency":"not yet assigned"},"database_specific":{"source":"https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2026-33018.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:L/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H"}]}