DEBIAN-CVE-2026-33023
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.
DEBIAN-CVE-2026-33023
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-2026-33023
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-2026-33023.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-2026-33023.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-2026-33023.json"
},
"ecosystem_specific": {
"urgency": "not yet assigned"
}
}
]Publisher severity
No explicit severity was provided.
- Event
- #56370 · Revision 1
- Added to Heist Feed
- Publisher date