Vulnerability Description
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 Score
MEDIUM
Related Weaknesses (CWE)
References
- https://github.com/thephpleague/commonmark/commit/493a5aa7d65754b73846006eaff9c2
- https://github.com/thephpleague/commonmark/releases/tag/2.9.0
- https://github.com/thephpleague/commonmark/security/advisories/GHSA-29pj-957v-52
- https://github.com/thephpleague/commonmark/security/advisories/GHSA-29pj-957v-52
FAQ
What is CVE-2026-71478?
CVE-2026-71478 is a vulnerability with a CVSS score of 6.1 (MEDIUM). 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...
How severe is CVE-2026-71478?
CVE-2026-71478 has been rated MEDIUM with a CVSS base score of 6.1/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2026-71478?
Check the references section above for vendor advisories and patch information. Review vendor security bulletins for remediation guidance.