DEBIAN-CVE-2026-33018
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->pixels 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.
DEBIAN-CVE-2026-33018
Primary source · Revision 1
Imported from structured advisory data. Source references identify upstream records or fields; verify affected versions and your deployed configuration.
Security context
Source reference: osv:DEBIAN-CVE-2026-33018
libsixel
Source reference: /affected/0/package/name
- Affected versions
- 1.10.3-3
Source reference:
/affected/0/versions1.10.5-1Source reference:
/affected/0/versions1:1.8.7-1Source reference:
/affected/0/versions1:1.8.7-2Source reference:
/affected/0/versions1:1.8.7-3Source reference:
/affected/0/versions1:1.8.7-4Source reference:
/affected/0/versions1:1.8.7-5Source reference:
/affected/0/versions1:1.8.7-6Source reference:
/affected/0/versions1:1.8.7-r2-1Source reference:
/affected/0/versions - Fixed versions
- Not stated in this record
- Prerequisites
- Not stated in this record
libsixel
Source reference: /affected/1/package/name
- Affected versions
- 1.10.5-1
Source reference:
/affected/1/versions1:1.8.7-1Source reference:
/affected/1/versions1:1.8.7-2Source reference:
/affected/1/versions1:1.8.7-3Source reference:
/affected/1/versions1:1.8.7-4Source reference:
/affected/1/versions1:1.8.7-5Source reference:
/affected/1/versions1:1.8.7-6Source reference:
/affected/1/versions1:1.8.7-r2-1Source reference:
/affected/1/versions - Fixed versions
- Not stated in this record
- Prerequisites
- Not stated in this record
libsixel
Source reference: /affected/2/package/name
- Affected versions
- 1.10.5-1
Source reference:
/affected/2/versions1:1.8.7-1Source reference:
/affected/2/versions1:1.8.7-2Source reference:
/affected/2/versions1:1.8.7-3Source reference:
/affected/2/versions1:1.8.7-4Source reference:
/affected/2/versions1:1.8.7-5Source reference:
/affected/2/versions1:1.8.7-6Source reference:
/affected/2/versions - Fixed versions
- 1:1.8.7-r2-1
Source reference:
/affected/2/ranges - Prerequisites
- Not stated in this record
Structured affected-version data
Original package identities and version rules from this source.
[
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
}
]
}
],
"package": {
"name": "libsixel",
"purl": "pkg:deb/debian/libsixel?arch=source&distro=bookworm",
"ecosystem": "Debian:12"
},
"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"
],
"database_specific": {
"source": "https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2026-33018.json"
},
"ecosystem_specific": {
"urgency": "not yet assigned"
}
},
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
}
]
}
],
"package": {
"name": "libsixel",
"purl": "pkg:deb/debian/libsixel?arch=source&distro=trixie",
"ecosystem": "Debian:13"
},
"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"
],
"database_specific": {
"source": "https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2026-33018.json"
},
"ecosystem_specific": {
"urgency": "not yet assigned"
}
},
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
},
{
"fixed": "1:1.8.7-r2-1"
}
]
}
],
"package": {
"name": "libsixel",
"purl": "pkg:deb/debian/libsixel?arch=source&distro=forky",
"ecosystem": "Debian:14"
},
"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"
],
"database_specific": {
"source": "https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2026-33018.json"
},
"ecosystem_specific": {
"urgency": "not yet assigned"
}
}
]Publisher severity
No explicit severity was provided.
- Event
- #56761 · Revision 1
- Added to Heist Feed
- Publisher date