CVE-2026-71478
league/commonmark: AttributesExtension href/src unsafe-link filter bypass via embedded control bytes
MEDIUM 6.1
At a glance
- Source
- NVD
- EPSS
- EPSS 0.36 % · percentile 29 ()
- State
- PUBLISHED
- Published
- Updated
- Assigner
- GitHub_M
- NVD status
- Awaiting Analysis
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.
Weaknesses (CWE)
- CWE-79 — Improper Neutralization of Input During Web Page Generation
- CWE-86 — Improper Neutralization of Invalid Characters in Identifiers in Web Pages
- CWE-692 — Incomplete Denylist to Cross-Site Scripting
References
Scores
| Version | Score | Vector | Scored by |
|---|---|---|---|
| CVSS 3.1 | MEDIUM 6.1 | CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N | GitHub_M |
| CVSS 3.1 | MEDIUM 6.1 | CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N | NVD · security-advisories@github.com (Secondary) |
Advisories
- GHSA-29pj-957v-52mc — league/commonmark: AttributesExtension href/src unsafe-link filter bypass via embedded control bytes
European references
- ENISA EUVD · EUVD-2026-54261
- GCVE · GCVE-0-2026-71478
Affected products
| Product | Versions |
|---|---|
| thephpleague · commonmark | affected >= 1.5.0, <= 2.8.3 |
Sources
| Source | Licence |
|---|---|
| CVE List (CVEProject cvelistV5) | CVE Program Terms of Use |
| EPSS (FIRST.org) | FIRST — attribution requested |
| ENISA EUVD | ENISA — reproduction authorised, source acknowledged |
| NVD (NIST) via fkie-cad/nvd-json-data-feeds | Public domain — this product uses data from the NVD API but is not endorsed or certified by the NVD |