league/commonmark: AttributesExtension href/src unsafe-link filter bypass via embedded control bytes

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-71478
StatePUBLISHED
AssignerGitHub_M
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-08-06 22:18:31 UTC
Updated2026-08-06 22:18:31 UTC
Descriptionleague/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.

Risk And Classification

Primary CVSS: v3.1 6.1 MEDIUM from [email protected]

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

Problem Types: CWE-79 | CWE-86 | CWE-692 | CWE-79 CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') | CWE-86 CWE-86: Improper Neutralization of Invalid Characters in Identifiers in Web Pages | CWE-692 CWE-692: Incomplete Denylist to Cross-Site Scripting

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary6.1MEDIUMCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
3.1CNADECLARED6.1MEDIUMCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
Required
Scope
Changed
Confidentiality
Low
Integrity
Low
Availability
None

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Thephpleague Commonmark affected >= 1.5.0, <= 2.8.3 Not specified

References

ReferenceSourceLinkTags
github.com/thephpleague/commonmark/commit/493a5aa7d65754b73846006eaff9c2... [email protected] github.com
github.com/thephpleague/commonmark/security/advisories/GHSA-29pj-957v-52mc [email protected] github.com
github.com/thephpleague/commonmark/releases/tag/2.9.0 [email protected] github.com
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis

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