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Vulnerabilities

Vulnerability · CVE-2026-33347

league/commonmark is a PHP Markdown parser.

Published Mar 24, 2026 · catalog updated Jun 17, 2026 · league/commonmark is a PHP

Check if you run it

No confirmed exploitation is on record for CVE-2026-33347. EPSS is 0.32%. Act only if a listed version of league/commonmark is a PHP is installed.

Gaps on this record

  • The stored product name is a package slug. The name on this page is taken from the title (league/commonmark is a PHP).
  • No version range is stored. A customer cannot check an installed version against this record.
  • No vendor fix or required action is stored. Compare the linked advisory before you change production.
Severity
Medium6.3
Known exploitation
Not in CISA/VulnCheck KEV
EPSS
0.32%
Remediation
Advisory link
Affected products
cpe thephpleague/commonmark

league/commonmark is a PHP Markdown parser. From version 2.3.0 to before version 2.8.2, the DomainFilteringAdapter in the Embed extension is vulnerable to an allowlist bypass due to a missing hostname boundary assertion in the domain-matching regex. An attacker-controlled domain like youtube.com.evil passes the allowlist check when youtube.com is an allowed domain. This issue has been patched in version 2.8.2.

Are you affected?

Enter the version you run. The result uses only the ranges stored on this record.

The check returns affected, not affected, or incomplete. It does not guess a version that is missing from the record.

  • cpe thephpleague/commonmarkversion unspecified

How to fix CVE-2026-33347

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Should you patch?

No confirmed exploitation is on record for CVE-2026-33347. EPSS is 0.32%. Act only if a listed version of league/commonmark is a PHP is installed.

Which versions are affected?

Affected version ranges are not on this record. Compare the installed version with the linked vendor advisory before you change production.

What should an analyst verify?

CWE-185; CWE-79: Cross-site Scripting (XSS); CWE-918: Server-Side Request Forgery (SSRF). EPSS 0.32%. There is no CISA KEV listing. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.

Code

The project this record applies to. Exploit listings stay in References.

Timeline

Detection, updates, and resolution for this record.

  1. Mar 24, 2026 · NIST NVD

    Detected

    league/commonmark is a PHP Markdown parser. From version 2.3.0 to before version 2.8.2, the DomainFilteringAdapter in the Embed extension is vulnerable to an allowlist bypass due to a missing hostname boundary assertion in the domain-matching regex. An attacker-controlled domain like youtube.com.evil passes the allowlist check when youtube.com is an allowed domain. This issue has been patched in v

  2. Jun 17, 2026 · NIST NVD

    Updated

    league/commonmark is a PHP Markdown parser. From version 2.3.0 to before version 2.8.2, the DomainFilteringAdapter in the Embed extension is vulnerable to an allowlist bypass due to a missing hostname boundary assertion in the domain-matching regex. An attacker-controlled domain like youtube.com.evil passes the allowlist check when youtube.com is an allowed domain. This issue has been patched in v

Sources

  • CVE.orgVulnerability recordCVE-2026-33347

    Official CVE identifier

    cve.org
  • FIRST EPSSExploitation probabilityCVE-2026-33347

    30-day exploitation probability 0.3%

    first.org
  • NIST NVDVulnerability recordCVE-2026-33347

    league/commonmark is a PHP Markdown parser. From version 2.3.0 to before version 2.8.2, the DomainFilteringAdapter in the Embed extension is vulnerable to an allowlist bypass due to a missing hostname boundary assertion in the domain-matching regex. An attacker-controlled domain

    nvd.nist.gov

References

Freshness

Last verified in this catalog Oct 18, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.