UBUNTU-CVE-2026-71478 (CVE-2026-71478)
Vulnerability from osv_ubuntu – Published: 2026-08-06 22:18 – Updated: 2026-08-13 00:14 – Source website
VLAI
Details
league/commonmark is a PHP library for parsing and rendering CommonMark Markdown. From 1.5.0 until 2.9.0, the AttributesExtension's href and src unsafe-link filter can be bypassed by embedding control bytes, such as a tab, carriage return, line feed, or leading C0 control character, in a javascript: URL that browsers discard before parsing the scheme, causing the browser to still execute the script even when the unsafe-link filter is enabled. This issue is fixed in 2.9.0.
Severity
6.1 (Medium)
N/A (UNKNOWN)
{
"affected": [
{
"ecosystem_specific": {
"binaries": [
{
"binary_name": "markdown",
"binary_version": "1.0.1-8"
}
]
},
"package": {
"ecosystem": "Ubuntu:16.04:LTS",
"name": "markdown",
"purl": "pkg:deb/ubuntu/markdown@1.0.1-8?arch=source\u0026distro=xenial"
},
"ranges": [
{
"events": [
{
"introduced": "0"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"1.0.1-7",
"1.0.1-8"
]
},
{
"ecosystem_specific": {
"binaries": [
{
"binary_name": "markdown",
"binary_version": "1.0.1-10"
}
]
},
"package": {
"ecosystem": "Ubuntu:18.04:LTS",
"name": "markdown",
"purl": "pkg:deb/ubuntu/markdown@1.0.1-10?arch=source\u0026distro=bionic"
},
"ranges": [
{
"events": [
{
"introduced": "0"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"1.0.1-9",
"1.0.1-10"
]
},
{
"ecosystem_specific": {
"binaries": [
{
"binary_name": "markdown",
"binary_version": "1.0.1-10"
}
]
},
"package": {
"ecosystem": "Ubuntu:20.04:LTS",
"name": "markdown",
"purl": "pkg:deb/ubuntu/markdown@1.0.1-10?arch=source\u0026distro=focal"
},
"ranges": [
{
"events": [
{
"introduced": "0"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"1.0.1-10"
]
},
{
"ecosystem_specific": {
"binaries": [
{
"binary_name": "python3-commonmark",
"binary_version": "0.9.1-3"
}
]
},
"package": {
"ecosystem": "Ubuntu:22.04:LTS",
"name": "commonmark",
"purl": "pkg:deb/ubuntu/commonmark@0.9.1-3?arch=source\u0026distro=jammy"
},
"ranges": [
{
"events": [
{
"introduced": "0"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"0.9.1-3"
]
},
{
"ecosystem_specific": {
"binaries": [
{
"binary_name": "markdown",
"binary_version": "1.0.1-10.1"
}
]
},
"package": {
"ecosystem": "Ubuntu:22.04:LTS",
"name": "markdown",
"purl": "pkg:deb/ubuntu/markdown@1.0.1-10.1?arch=source\u0026distro=jammy"
},
"ranges": [
{
"events": [
{
"introduced": "0"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"1.0.1-10.1"
]
},
{
"ecosystem_specific": {
"binaries": [
{
"binary_name": "python3-commonmark",
"binary_version": "0.9.1-5"
}
]
},
"package": {
"ecosystem": "Ubuntu:24.04:LTS",
"name": "commonmark",
"purl": "pkg:deb/ubuntu/commonmark@0.9.1-5?arch=source\u0026distro=noble"
},
"ranges": [
{
"events": [
{
"introduced": "0"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"0.9.1-4",
"0.9.1-5"
]
},
{
"ecosystem_specific": {
"binaries": [
{
"binary_name": "markdown",
"binary_version": "1.0.1-12"
}
]
},
"package": {
"ecosystem": "Ubuntu:24.04:LTS",
"name": "markdown",
"purl": "pkg:deb/ubuntu/markdown@1.0.1-12?arch=source\u0026distro=noble"
},
"ranges": [
{
"events": [
{
"introduced": "0"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"1.0.1-12"
]
},
{
"ecosystem_specific": {
"binaries": [
{
"binary_name": "python3-commonmark",
"binary_version": "0.9.1-8build1"
}
]
},
"package": {
"ecosystem": "Ubuntu:26.04:LTS",
"name": "commonmark",
"purl": "pkg:deb/ubuntu/commonmark@0.9.1-8build1?arch=source\u0026distro=resolute"
},
"ranges": [
{
"events": [
{
"introduced": "0"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"0.9.1-8",
"0.9.1-8build1"
]
},
{
"ecosystem_specific": {
"binaries": [
{
"binary_name": "markdown",
"binary_version": "1.0.1-14"
}
]
},
"package": {
"ecosystem": "Ubuntu:26.04:LTS",
"name": "markdown",
"purl": "pkg:deb/ubuntu/markdown@1.0.1-14?arch=source\u0026distro=resolute"
},
"ranges": [
{
"events": [
{
"introduced": "0"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"1.0.1-14"
]
}
],
"aliases": [],
"details": "league/commonmark is a PHP library for parsing and rendering CommonMark Markdown. From 1.5.0 until 2.9.0, the AttributesExtension\u0027s href and src unsafe-link filter can be bypassed by embedding control bytes, such as a tab, carriage return, line feed, or leading C0 control character, in a javascript: URL that browsers discard before parsing the scheme, causing the browser to still execute the script even when the unsafe-link filter is enabled. This issue is fixed in 2.9.0.",
"id": "UBUNTU-CVE-2026-71478",
"modified": "2026-08-13T00:14:08Z",
"published": "2026-08-06T22:18:00Z",
"references": [
{
"type": "REPORT",
"url": "https://ubuntu.com/security/CVE-2026-71478"
},
{
"type": "REPORT",
"url": "https://www.cve.org/CVERecord?id=CVE-2026-71478"
},
{
"type": "REPORT",
"url": "https://github.com/thephpleague/commonmark/commit/493a5aa7d65754b73846006eaff9c2c4431a8e2c"
},
{
"type": "REPORT",
"url": "https://github.com/thephpleague/commonmark/releases/tag/2.9.0"
},
{
"type": "REPORT",
"url": "https://github.com/thephpleague/commonmark/security/advisories/GHSA-29pj-957v-52mc"
}
],
"related": [],
"schema_version": "1.7.0",
"severity": [
{
"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-2026-71478"
]
}
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Sightings
| Author | Source | Type | Date | Other |
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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.
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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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