UBUNTU-CVE-2026-44637 (CVE-2026-44637)
Vulnerability from osv_ubuntu – Published: 2026-05-14 20:17 – Updated: 2026-05-14 20:17 – Source website
VLAI
Details
libsixel is a SIXEL encoder/decoder implementation derived from kmiya's sixel. From to 1.8.7-r1, a signed integer overflow in the SIXEL parser's image-buffer doubling loop can lead to an out-of-bounds heap write in sixel_decode_raw_impl. context->pos_x grows by repeat_count on every sixel character with no upper bound check. Once pos_x approaches INT_MAX, the expression "pos_x + repeat_count" used to size the image buffer overflows signed int. Depending on how the overflow wraps, the resize check that should reject oversized buffers can be bypassed, after which a subsequent write computes a large attacker-influenced offset into image->data and writes past the allocation. Reachable from any caller that decodes attacker-supplied SIXEL data, including img2sixel. This vulnerability is fixed in 1.8.7-r2.
Severity
7.1 (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. From to 1.8.7-r1, a signed integer overflow in the SIXEL parser\u0027s image-buffer doubling loop can lead to an out-of-bounds heap write in sixel_decode_raw_impl. context-\u003epos_x grows by repeat_count on every sixel character with no upper bound check. Once pos_x approaches INT_MAX, the expression \"pos_x + repeat_count\" used to size the image buffer overflows signed int. Depending on how the overflow wraps, the resize check that should reject oversized buffers can be bypassed, after which a subsequent write computes a large attacker-influenced offset into image-\u003edata and writes past the allocation. Reachable from any caller that decodes attacker-supplied SIXEL data, including img2sixel. This vulnerability is fixed in 1.8.7-r2.",
"id": "UBUNTU-CVE-2026-44637",
"modified": "2026-05-14T20:17:00Z",
"published": "2026-05-14T20:17:00Z",
"references": [
{
"type": "REPORT",
"url": "https://ubuntu.com/security/CVE-2026-44637"
},
{
"type": "REPORT",
"url": "https://www.cve.org/CVERecord?id=CVE-2026-44637"
},
{
"type": "REPORT",
"url": "https://github.com/saitoha/libsixel/security/advisories/GHSA-9jm7-77gr-qghv"
}
],
"related": [],
"schema_version": "1.7.0",
"severity": [
{
"score": "CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:H",
"type": "CVSS_V3"
},
{
"score": "medium",
"type": "Ubuntu"
}
],
"upstream": [
"CVE-2026-44637"
]
}
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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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