Medium 6.1Published Aug 6, 2026

CVE-2026-71478league/commonmark: AttributesExtension href/src unsafe-link filter bypass via embedded control bytes

Updated under an hour ago (2026-10-19 08:20 UTC)

Does this affect you?

It affects thephpleague commonmark. Add what you run to find out whether that includes you.

No exploitation reported and no EPSS estimate yet.

Do this next

Start free and add your stack

Free account, 1 product

Every CVE for thephpleague commonmark

Exploited in the last 30 days

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: 6.1 MEDIUM (v3.1, CNA)CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
Weakness (CWE): CWE-79, CWE-86, CWE-692
Known exploited: Not in CISA's KEV catalog
EPSS (exploitation in the next 30 days): Not loaded for this CVE
Assigned by: GitHub_M
NVD analysis: Awaiting Analysis
Record last updated: Aug 7, 2026
First seen by InfoSec Signals: Oct 9, 2026

Affected products

Affected products

thephpleague commonmark thephpleague:commonmark (from the name)	from 1.5.0, <= 2.8.3	CNA record

References

https://github.com/thephpleague/commonmark/security/advisories/GHSA-29pj-957v-52mcx-refsource-confirm
https://github.com/thephpleague/commonmark/commit/493a5aa7d65754b73846006eaff9c2c4431a8e2cx-refsource-misc
https://github.com/thephpleague/commonmark/releases/tag/2.9.0x-refsource-misc

The CVE record on cve.org NVD's entry

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.