What is CVE-2026-30838?

CVE-2026-30838 is a medium-severity vulnerability in Thephpleague Commonmark, classified under Cross-site Scripting. CVSS score: 6.1/10. Published 2026-03-07.

How severe is CVE-2026-30838?

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

XSS in Thephpleague Commonmark

CVE-2026-30838

league/commonmark is a PHP Markdown parser. Prior to version 2.8.1, the DisallowedRawHtml extension can be bypassed by inserting a newline, tab, or other ASCII whitespace character between a disallowed HTML tag name and the closing >. For…

Vulnerability class: XSS (Cross-Site Scripting)

EPSS: 0.002 (12.3th percentile) — read the EPSS interpretation.

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 < 2.8.1

Weakness classification (CWE)

CWE-79 — Cross-site Scripting

References

security-advisories@github.com (x_refsource_CONFIRM, Mitigation, Vendor Advisory)

Frequently asked questions

What is CVE-2026-30838?: CVE-2026-30838 is a medium-severity vulnerability in Thephpleague Commonmark, classified under Cross-site Scripting. CVSS score: 6.1/10. Published 2026-03-07.
How severe is CVE-2026-30838?: Medium severity. CVSS v3 base score is 6.1 out of 10.