UBUNTU-CVE-2026-33023 (CVE-2026-33023)
Vulnerability from osv_ubuntu – Published: 2026-04-14 23:16 – Updated: 2026-05-20 15:27 – Source website
VLAI
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.
Severity
7.8 (High)
N/A (UNKNOWN)
References
{
"affected": [
{
"ecosystem_specific": {
"binaries": [
{
"binary_name": "libsixel-bin",
"binary_version": "1.5.2-2"
},
{
"binary_name": "libsixel1",
"binary_version": "1.5.2-2"
}
]
},
"package": {
"ecosystem": "Ubuntu:16.04:LTS",
"name": "libsixel",
"purl": "pkg:deb/ubuntu/libsixel@1.5.2-2?arch=source\u0026distro=xenial"
},
"ranges": [
{
"events": [
{
"introduced": "0"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"1.4.2-1",
"1.5.2-2"
]
},
{
"ecosystem_specific": {
"binaries": [
{
"binary_name": "libsixel-bin",
"binary_version": "1.7.3-1"
},
{
"binary_name": "libsixel-examples",
"binary_version": "1.7.3-1"
},
{
"binary_name": "libsixel1",
"binary_version": "1.7.3-1"
}
]
},
"package": {
"ecosystem": "Ubuntu:18.04:LTS",
"name": "libsixel",
"purl": "pkg:deb/ubuntu/libsixel@1.7.3-1?arch=source\u0026distro=bionic"
},
"ranges": [
{
"events": [
{
"introduced": "0"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"1.5.2-2",
"1.7.3-1"
]
},
{
"ecosystem_specific": {
"binaries": [
{
"binary_name": "libsixel-bin",
"binary_version": "1.8.2-2.1"
},
{
"binary_name": "libsixel-examples",
"binary_version": "1.8.2-2.1"
},
{
"binary_name": "libsixel1",
"binary_version": "1.8.2-2.1"
}
]
},
"package": {
"ecosystem": "Ubuntu:20.04:LTS",
"name": "libsixel",
"purl": "pkg:deb/ubuntu/libsixel@1.8.2-2.1?arch=source\u0026distro=focal"
},
"ranges": [
{
"events": [
{
"introduced": "0"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"1.8.2-1",
"1.8.2-2.1"
]
},
{
"ecosystem_specific": {
"binaries": [
{
"binary_name": "libsixel-bin",
"binary_version": "1.10.3-3"
},
{
"binary_name": "libsixel-examples",
"binary_version": "1.10.3-3"
},
{
"binary_name": "libsixel1",
"binary_version": "1.10.3-3"
}
]
},
"package": {
"ecosystem": "Ubuntu:22.04:LTS",
"name": "libsixel",
"purl": "pkg:deb/ubuntu/libsixel@1.10.3-3?arch=source\u0026distro=jammy"
},
"ranges": [
{
"events": [
{
"introduced": "0"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"1.8.6-2",
"1.10.3-2",
"1.10.3-3"
]
},
{
"ecosystem_specific": {
"binaries": [
{
"binary_name": "libsixel-bin",
"binary_version": "1.10.3-3build1"
},
{
"binary_name": "libsixel-examples",
"binary_version": "1.10.3-3build1"
},
{
"binary_name": "libsixel1",
"binary_version": "1.10.3-3build1"
}
]
},
"package": {
"ecosystem": "Ubuntu:24.04:LTS",
"name": "libsixel",
"purl": "pkg:deb/ubuntu/libsixel@1.10.3-3build1?arch=source\u0026distro=noble"
},
"ranges": [
{
"events": [
{
"introduced": "0"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"1.10.3-3",
"1.10.3-3build1"
]
},
{
"ecosystem_specific": {
"binaries": [
{
"binary_name": "libsixel-bin",
"binary_version": "1.10.5-1"
},
{
"binary_name": "libsixel-examples",
"binary_version": "1.10.5-1"
},
{
"binary_name": "libsixel1",
"binary_version": "1.10.5-1"
}
]
},
"package": {
"ecosystem": "Ubuntu:25.10",
"name": "libsixel",
"purl": "pkg:deb/ubuntu/libsixel@1.10.5-1?arch=source\u0026distro=questing"
},
"ranges": [
{
"events": [
{
"introduced": "0"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"1.10.5-1"
]
},
{
"ecosystem_specific": {
"binaries": [
{
"binary_name": "libsixel-bin",
"binary_version": "1.10.5-1build1"
},
{
"binary_name": "libsixel-examples",
"binary_version": "1.10.5-1build1"
},
{
"binary_name": "libsixel1",
"binary_version": "1.10.5-1build1"
}
]
},
"package": {
"ecosystem": "Ubuntu:26.04:LTS",
"name": "libsixel",
"purl": "pkg:deb/ubuntu/libsixel@1.10.5-1build1?arch=source\u0026distro=resolute"
},
"ranges": [
{
"events": [
{
"introduced": "0"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"1.10.5-1",
"1.10.5-1build1"
]
}
],
"aliases": [],
"details": "libsixel is a SIXEL encoder/decoder implementation derived from kmiya\u0027s 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.",
"id": "UBUNTU-CVE-2026-33023",
"modified": "2026-05-20T15:27:21Z",
"published": "2026-04-14T23:16:00Z",
"references": [
{
"type": "REPORT",
"url": "https://ubuntu.com/security/CVE-2026-33023"
},
{
"type": "REPORT",
"url": "https://www.cve.org/CVERecord?id=CVE-2026-33023"
},
{
"type": "REPORT",
"url": "https://github.com/saitoha/libsixel/security/advisories/GHSA-hr25-g2j6-qjw6"
},
{
"type": "REPORT",
"url": "https://github.com/saitoha/libsixel/releases/tag/v1.8.7-r1"
}
],
"related": [],
"schema_version": "1.7.0",
"severity": [
{
"score": "CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H",
"type": "CVSS_V3"
},
{
"score": "medium",
"type": "Ubuntu"
}
],
"upstream": [
"CVE-2026-33023"
]
}
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| Author | Source | Type | Date | Other |
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The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
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