CVE-2026-71478

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.

CVSS v3 6.1 MEDIUM

6.1^/10

CVSS v3 : MEDIUM

Vector :

Exploitability : 2.8 / Impact : 2.7

Attack Vector NETWORK

Attack Complexity LOW

Privileges Required NONE

User Interaction REQUIRED

Confidentiality Impact LOW

Integrity Impact LOW

Availability Impact NONE

Scope CHANGED

References

Link	Resource
https://github.com/thephpleague/commonmark/commit/493a5aa7d65754b73846006eaff9c2c4431a8e2c
https://github.com/thephpleague/commonmark/releases/tag/2.9.0
https://github.com/thephpleague/commonmark/security/advisories/GHSA-29pj-957v-52mc
https://github.com/thephpleague/commonmark/security/advisories/GHSA-29pj-957v-52mc

Configurations

No configuration.

History

No history.

Information

Published : 2026-08-06 22:18

Updated : 2026-09-10 20:41

NVD link : CVE-2026-71478

Mitre link : CVE-2026-71478

CVE.ORG link : CVE-2026-71478

JSON object : View

Products Affected

No product.

CWE

CWE-79

Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

CWE-86

Improper Neutralization of Invalid Characters in Identifiers in Web Pages

CWE-692

Incomplete Denylist to Cross-Site Scripting

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