CVE-2026-71478CWE-692CWE-79CWE-86cross-site-scripting

CVE-2026-71478

Medium · published August 7, 2026

CVSS v3.1
6.1
EPSS
0%
Percentile
10.0
In the wild
Unconfirmed
What it is

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.

The record
Technical detail
CVSS v3.1
6.1 · MEDIUM
Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
CVSS v4.0
Not supplied
EPSS
0.00201 · 10.0th percentile
Weaknesses
CWE-692 · Incomplete Denylist to Cross-Site Scripting; 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
Published
2026-08-07T02:18Z
References (4)
https://github.com/thephpleague/commonmark/commit/493a5aa7d65754b73846006eaff9c2c4431a8e2c · [email protected]https://github.com/thephpleague/commonmark/releases/tag/2.9.0 · [email protected]https://github.com/thephpleague/commonmark/security/advisories/GHSA-29pj-957v-52mc · [email protected]https://github.com/thephpleague/commonmark/security/advisories/GHSA-29pj-957v-52mc · 134c704f-9b21-4f2e-91b3-4a467353bcc0
EPSS history
Timeline
  • 06 AUG 20:30Z
    league/commonmark: AttributesExtension href/src unsafe-link filter bypass via embedded control bytes
    cvelistv5