What is CVE-2026-71478?

CVE-2026-71478 is a medium-severity vulnerability in Thephpleague Commonmark, classified under Cross-site Scripting. CVSS score: 6.1/10. Published 2026-08-06.

How severe is CVE-2026-71478?

Medium severity. CVSS v3 base score is 6.1 out of 10.

XSS in Thephpleague Commonmark

CVE-2026-71478

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…

Vulnerability class: XSS (Cross-Site Scripting)

CVSS v3 metric

CVSS v3 base score 6.1 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N.

Affected products

Thephpleague Commonmark — versions >= 1.5.0, <= 2.8.3

Weakness classification (CWE)

References

security-advisories@github.com (x_refsource_MISC)
security-advisories@github.com (x_refsource_MISC)
security-advisories@github.com (x_refsource_CONFIRM)

Frequently asked questions

What is CVE-2026-71478?: CVE-2026-71478 is a medium-severity vulnerability in Thephpleague Commonmark, classified under Cross-site Scripting. CVSS score: 6.1/10. Published 2026-08-06.
How severe is CVE-2026-71478?: Medium severity. CVSS v3 base score is 6.1 out of 10.