CVE-2026-30838: CommonMark has DisallowedRawHtml extension bypass via whitespace in HTML tag names

CVE-2026-30838 · Severity: medium · CVSS 4 · Published 2026-03-06

CommonMark has DisallowedRawHtml extension bypass via whitespace in HTML tag names

Technologies: league/commonmark (Packagist). Vendors: Packagist.

Quick answers

Is CVE-2026-30838 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-30838 being exploited in the wild.
How severe is CVE-2026-30838?
Medium severity, with a CVSS score of 4, published 6 March 2026.
Which products and versions are affected?
league/commonmark (Packagist) ECOSYSTEM:introduced=2.0.0,fixed=2.8.1.
Is there a fix for CVE-2026-30838?
Yes. league/commonmark (Packagist): upgrade to 2.8.1 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
Am I affected by CVE-2026-30838?
Check whether you run league/commonmark (Packagist) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

How to fix

  • league/commonmark (Packagist): upgrade to 2.8.1 or later
    composer require league/commonmark:^2.8.1

Affected products

  • league/commonmark (Packagist) ECOSYSTEM:introduced=2.0.0,fixed=2.8.1

Identifiers

  • CVE-2026-30838
  • GHSA-4v6x-c7xx-hw9f

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