UBUNTU-CVE-2026-86431

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Source
https://ubuntu.com/security/CVE-2026-86431
Import Source
https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-86431.json
JSON Data
https://api.test.osv.dev/v1/vulns/UBUNTU-CVE-2026-86431
Upstream
Published
2026-09-07T13:20:00Z
Modified
2026-09-16T14:02:38Z
Severity
  • 7.2 (High) CVSS_V3 - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:N CVSS Calculator
  • 6.9 (Medium) CVSS_V4 - CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:L/VA:N/SC:L/SI:L/SA:N CVSS Calculator
  • Ubuntu - medium
Summary
[none]
Details

league/commonmark (thephpleague/commonmark) versions >= 2.7.0 and < 2.9.1 contain a cross-site scripting vulnerability in the AttributesExtension. Prefixing an attribute name with a single U+000C form feed byte (e.g. {\x0Conclick="alert(1)"}) bypasses the AttributesHelper::filterAttributes() 'on*' event-handler filter because PHP's trim() does not strip U+000C, causing the attribute to be written verbatim into the output where browsers parse it as a genuine event handler. The same prefix also defeats the allow_unsafe_links check, allowing javascript: URIs through href/src attributes even when allow_unsafe_links is false. Exploitation requires processing untrusted Markdown with the AttributesExtension enabled; the injected script executes when the rendered HTML is viewed. Fixed in 2.9.1.

References

Affected packages

Ubuntu:Pro:20.04:LTS / php-league-commonmark

Package

Name
php-league-commonmark
Purl
pkg:deb/ubuntu/php-league-commonmark?arch=source&distro=esm-apps%2Ffocal

Affected ranges

Type
ECOSYSTEM
Events
Introduced
0 Unknown introduced version / All previous versions are affected

Affected versions

1.*
1.1.2-1
1.2.0-1
1.3.0-1
1.3.1-1
1.3.1-1ubuntu2
1.3.1-1ubuntu2+esm1

Ecosystem specific 

{
    "binaries":  [
        {
            "binary_name":  "php-league-commonmark",
            "binary_version":  "1.3.1-1ubuntu2+esm1"
        }
    ]
}

Database specific

source 
"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-86431.json"

Ubuntu:Pro:22.04:LTS / php-league-commonmark

Package

Name
php-league-commonmark
Purl
pkg:deb/ubuntu/php-league-commonmark?arch=source&distro=esm-apps%2Fjammy

Affected ranges

Type
ECOSYSTEM
Events
Introduced
0 Unknown introduced version / All previous versions are affected

Affected versions

1.*
1.5.7-2build1
1.6.6-1build1
1.6.7-1
1.6.7-1ubuntu0.1~esm1

Ecosystem specific 

{
    "binaries":  [
        {
            "binary_name":  "php-league-commonmark",
            "binary_version":  "1.6.7-1ubuntu0.1~esm1"
        }
    ]
}

Database specific

source 
"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-86431.json"

Ubuntu:Pro:24.04:LTS / php-league-commonmark

Package

Name
php-league-commonmark
Purl
pkg:deb/ubuntu/php-league-commonmark?arch=source&distro=esm-apps%2Fnoble

Affected ranges

Type
ECOSYSTEM
Events
Introduced
0 Unknown introduced version / All previous versions are affected

Affected versions

2.*
2.3.9-1
2.4.1-1
2.4.2-1
2.4.2-2
2.4.2-2ubuntu0.1~esm1

Ecosystem specific 

{
    "binaries":  [
        {
            "binary_name":  "php-league-commonmark",
            "binary_version":  "2.4.2-2ubuntu0.1~esm1"
        }
    ]
}

Database specific

source 
"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-86431.json"

Ubuntu:26.04:LTS / php-league-commonmark

Package

Name
php-league-commonmark
Purl
pkg:deb/ubuntu/php-league-commonmark?arch=source&distro=resolute

Affected ranges

Type
ECOSYSTEM
Events
Introduced
0 Unknown introduced version / All previous versions are affected

Affected versions

2.*
2.7.0-1
2.7.1-2
2.8.0-1

Ecosystem specific 

{
    "binaries":  [
        {
            "binary_name":  "php-league-commonmark",
            "binary_version":  "2.8.0-1"
        }
    ]
}

Database specific

source 
"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-86431.json"