# CVE-2026-71478

## Summary

- **CVE ID:** CVE-2026-71478
- **Severity:** MEDIUM
- **CVSS Score:** 6.1 (CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N)
- **CWE:** CWE-79, CWE-86, CWE-692
- **Published:** Aug 6, 2026
- **Last Modified:** Aug 7, 2026

## 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.

## Affected Products

- thephpleague — commonmark (>= 1.5.0, <= 2.8.3)

## References

- [CNA](https://github.com/thephpleague/commonmark/security/advisories/GHSA-29pj-957v-52mc)
- [CNA](https://github.com/thephpleague/commonmark/commit/493a5aa7d65754b73846006eaff9c2c4431a8e2c)
- [CNA](https://github.com/thephpleague/commonmark/releases/tag/2.9.0)

## Exploitation Prediction (EPSS)

- **EPSS Score:** 0.20%
- **EPSS Percentile:** 10.0

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_Exported from OnDuty AI Vulnerability Intelligence on 2026-09-10._