CVE-2026-30838: league/commonmark is a PHP Markdown parser

Q: How do I fix CVE-2026-30838?

commonmark: upgrade to 2.8.1. Exact commands for each OS are on this page.

Q: Is CVE-2026-30838 being exploited?

CVE-2026-30838 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2026-30838 affect?

CVE-2026-30838 affects commonmark. Severity is medium (CVSS 6.1). 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 e

Routine

MEDIUM 6.1UPGRADE

CVE-2026-30838 is a medium-severity flaw (CVSS 6.1) affecting commonmark. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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 example, <script\n> would pass through unfiltered and be rendered as a valid HTML tag by browsers. This is a cross-site scripting (XSS) vector for any application that relies on this extension to sanitize untrus

Why this priority

No elevated risk signals yet

A fixed release or distro patch exists.

Risk facts

CVSS score	6.1 (Medium)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	Required
EPSS exploit chance	0.2% (top 87%)
CISA exploited list	No
Weakness	CWE-79
Published	2026-03-07
Last modified	2026-06-17

Publisher (CNA): GitHub, Inc. · Vendor: thephpleague

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-03-07 16:15 UTCPublished CVE record published
2026-06-17 10:33 UTCUpdated Record last modified

thephpleague commonmark UPGRADE

Affected: < 2.8.1

Fixed in: 2.8.1

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy commonmark || rpm -q commonmark || commonmark --version

2. UPGRADE to 2.8.1 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade commonmark

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade commonmark

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-30838?

commonmark: upgrade to 2.8.1. Exact commands for each OS are on this page.

Is CVE-2026-30838 being exploited?

CVE-2026-30838 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-30838 affect?

CVE-2026-30838 affects commonmark. Severity is medium (CVSS 6.1). 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 e

How urgent is CVE-2026-30838?

Priority 25/100. No elevated risk signals yet.

Software pages

PHP vulnerabilities

Related CVEs

CVE-2026-33347 MEDIUM 6.1 UPGRADE league/commonmark is a PHP Markdown parser

References

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