DEBIAN-CVE-2026-86431

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Source
https://security-tracker.debian.org/tracker/CVE-2026-86431
Import Source
https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2026-86431.json
JSON Data
https://api.osv.dev/v1/vulns/DEBIAN-CVE-2026-86431
Upstream
Published
2026-09-07T13:20:42Z
Modified
2026-09-10T08:47:26Z
Severity
  • 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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X CVSS Calculator
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

Debian:12 / php-league-commonmark

Package

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

Affected ranges

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

Affected versions

2.*
2.3.9-1
2.3.9-1+deb12u1
2.4.0-1
2.4.1-1
2.4.2-1
2.4.2-2
2.5.0-1
2.5.1-1
2.5.3-1
2.6.0-1
2.6.1-1
2.6.1-2
2.6.2-1
2.7.0-1
2.7.1-1
2.7.1-2
2.8.0-1
2.8.1-1
2.8.2-1
2.8.2-2
2.8.3-1
2.9.0-1
2.10.0-1

Ecosystem specific 

{
    "urgency": "not yet assigned"
}

Database specific

source 
"https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2026-86431.json"

Debian:13 / php-league-commonmark

Package

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

Affected ranges

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

Affected versions

2.*
2.7.0-1
2.7.0-1+deb13u1
2.7.1-1
2.7.1-2
2.8.0-1
2.8.1-1
2.8.2-1
2.8.2-2
2.8.3-1
2.9.0-1
2.10.0-1

Ecosystem specific 

{
    "urgency": "not yet assigned"
}

Database specific

source 
"https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2026-86431.json"

Debian:14 / php-league-commonmark

Package

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

Affected ranges

Type
ECOSYSTEM
Events
Introduced
0 Unknown introduced version / All previous versions are affected
Fixed
2.10.0-1

Affected versions

2.*
2.7.0-1
2.7.1-1
2.7.1-2
2.8.0-1
2.8.1-1
2.8.2-1
2.8.2-2
2.8.3-1
2.9.0-1

Ecosystem specific 

{
    "urgency": "not yet assigned"
}

Database specific

source 
"https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2026-86431.json"