UBUNTU-CVE-2026-44899 (CVE-2026-44899)
Vulnerability from osv_ubuntu – Published: 2026-05-26 21:16 – Updated: 2026-05-29 17:49 – Source website
VLAI
Details
Mistune is a Python Markdown parser with renderers and plugins. Prior to 3.2.1, the Image directive plugin validates the :width: and :height: options with a regex compiled as _num_re = re.compile(r"^\d+(?:.\d*)?"). When the validated value is not a plain integer, render_block_image() inserts it directly into a style="width:...;" or style="height:...;" attribute. Because the value was accepted by the prefix-only regex, any CSS after the leading digits reaches the style= attribute verbatim and without escaping. This vulnerability is fixed in 3.2.1.
Severity
4.7 (Medium)
6.1 (Medium)
N/A (UNKNOWN)
References
{
"affected": [
{
"ecosystem_specific": {
"binaries": [
{
"binary_name": "python-mistune",
"binary_version": "0.7.1-1"
},
{
"binary_name": "python3-mistune",
"binary_version": "0.7.1-1"
}
]
},
"package": {
"ecosystem": "Ubuntu:16.04:LTS",
"name": "mistune",
"purl": "pkg:deb/ubuntu/mistune@0.7.1-1?arch=source\u0026distro=xenial"
},
"ranges": [
{
"events": [
{
"introduced": "0"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"0.6-2",
"0.7.1-1"
]
},
{
"ecosystem_specific": {
"binaries": [
{
"binary_name": "python-mistune",
"binary_version": "0.8.3-2"
},
{
"binary_name": "python3-mistune",
"binary_version": "0.8.3-2"
}
]
},
"package": {
"ecosystem": "Ubuntu:18.04:LTS",
"name": "mistune",
"purl": "pkg:deb/ubuntu/mistune@0.8.3-2?arch=source\u0026distro=bionic"
},
"ranges": [
{
"events": [
{
"introduced": "0"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"0.7.4-1",
"0.8-1",
"0.8.1-1",
"0.8.3-2"
]
},
{
"ecosystem_specific": {
"binaries": [
{
"binary_name": "python3-mistune",
"binary_version": "0.8.4-2"
}
]
},
"package": {
"ecosystem": "Ubuntu:20.04:LTS",
"name": "mistune",
"purl": "pkg:deb/ubuntu/mistune@0.8.4-2?arch=source\u0026distro=focal"
},
"ranges": [
{
"events": [
{
"introduced": "0"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"0.8.4-1",
"0.8.4-2"
]
},
{
"ecosystem_specific": {
"binaries": [
{
"binary_name": "python3-mistune",
"binary_version": "2.0.0-1+really0.8.4-1"
}
]
},
"package": {
"ecosystem": "Ubuntu:22.04:LTS",
"name": "mistune",
"purl": "pkg:deb/ubuntu/mistune@2.0.0-1+really0.8.4-1?arch=source\u0026distro=jammy"
},
"ranges": [
{
"events": [
{
"introduced": "0"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"0.8.4-4",
"0.8.4-5",
"2.0.0-1+really0.8.4-1"
]
},
{
"ecosystem_specific": {
"binaries": [
{
"binary_name": "python3-mistune0",
"binary_version": "0.8.4-2"
}
]
},
"package": {
"ecosystem": "Ubuntu:22.04:LTS",
"name": "mistune0",
"purl": "pkg:deb/ubuntu/mistune0@0.8.4-2?arch=source\u0026distro=jammy"
},
"ranges": [
{
"events": [
{
"introduced": "0"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"0.8.4-1",
"0.8.4-2"
]
},
{
"ecosystem_specific": {
"binaries": [
{
"binary_name": "python3-mistune",
"binary_version": "3.0.2-1"
}
]
},
"package": {
"ecosystem": "Ubuntu:24.04:LTS",
"name": "mistune",
"purl": "pkg:deb/ubuntu/mistune@3.0.2-1?arch=source\u0026distro=noble"
},
"ranges": [
{
"events": [
{
"introduced": "0"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"2.0.4-2",
"3.0.2-1"
]
},
{
"ecosystem_specific": {
"binaries": [
{
"binary_name": "python3-mistune0",
"binary_version": "0.8.4-2"
}
]
},
"package": {
"ecosystem": "Ubuntu:24.04:LTS",
"name": "mistune0",
"purl": "pkg:deb/ubuntu/mistune0@0.8.4-2?arch=source\u0026distro=noble"
},
"ranges": [
{
"events": [
{
"introduced": "0"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"0.8.4-2"
]
},
{
"ecosystem_specific": {
"binaries": [
{
"binary_name": "python3-mistune",
"binary_version": "3.1.3-1"
}
]
},
"package": {
"ecosystem": "Ubuntu:25.10",
"name": "mistune",
"purl": "pkg:deb/ubuntu/mistune@3.1.3-1?arch=source\u0026distro=questing"
},
"ranges": [
{
"events": [
{
"introduced": "0"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"3.0.2-2",
"3.1.3-1"
]
},
{
"ecosystem_specific": {
"binaries": [
{
"binary_name": "python3-mistune0",
"binary_version": "0.8.4-4"
}
]
},
"package": {
"ecosystem": "Ubuntu:25.10",
"name": "mistune0",
"purl": "pkg:deb/ubuntu/mistune0@0.8.4-4?arch=source\u0026distro=questing"
},
"ranges": [
{
"events": [
{
"introduced": "0"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"0.8.4-4"
]
},
{
"ecosystem_specific": {
"binaries": [
{
"binary_name": "python3-mistune",
"binary_version": "3.1.4-1"
}
]
},
"package": {
"ecosystem": "Ubuntu:26.04:LTS",
"name": "mistune",
"purl": "pkg:deb/ubuntu/mistune@3.1.4-1?arch=source\u0026distro=resolute"
},
"ranges": [
{
"events": [
{
"introduced": "0"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"3.1.3-1",
"3.1.4-1"
]
},
{
"ecosystem_specific": {
"binaries": [
{
"binary_name": "python3-mistune0",
"binary_version": "0.8.4-6"
}
]
},
"package": {
"ecosystem": "Ubuntu:26.04:LTS",
"name": "mistune0",
"purl": "pkg:deb/ubuntu/mistune0@0.8.4-6?arch=source\u0026distro=resolute"
},
"ranges": [
{
"events": [
{
"introduced": "0"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"0.8.4-4",
"0.8.4-5",
"0.8.4-6"
]
}
],
"aliases": [],
"details": "Mistune is a Python Markdown parser with renderers and plugins. Prior to 3.2.1, the Image directive plugin validates the :width: and :height: options with a regex compiled as _num_re = re.compile(r\"^\\d+(?:\\.\\d*)?\"). When the validated value is not a plain integer, render_block_image() inserts it directly into a style=\"width:...;\" or style=\"height:...;\" attribute. Because the value was accepted by the prefix-only regex, any CSS after the leading digits reaches the style= attribute verbatim and without escaping. This vulnerability is fixed in 3.2.1.",
"id": "UBUNTU-CVE-2026-44899",
"modified": "2026-05-29T17:49:36Z",
"published": "2026-05-26T21:16:00Z",
"references": [
{
"type": "REPORT",
"url": "https://ubuntu.com/security/CVE-2026-44899"
},
{
"type": "REPORT",
"url": "https://www.cve.org/CVERecord?id=CVE-2026-44899"
},
{
"type": "REPORT",
"url": "https://github.com/lepture/mistune/releases/tag/v3.2.1"
},
{
"type": "REPORT",
"url": "https://github.com/lepture/mistune/security/advisories/GHSA-ccfx-mfmx-2fx9"
}
],
"related": [],
"schema_version": "1.7.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:N/A:N",
"type": "CVSS_V3"
},
{
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N",
"type": "CVSS_V3"
},
{
"score": "medium",
"type": "Ubuntu"
}
],
"upstream": [
"CVE-2026-44899"
]
}
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Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
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The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the
vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base
model, served locally by ML-Gateway.
They have not been verified by an analyst and are provided for guidance only.
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.
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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Related by attack behaviour
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