Is CVE-2026-33347 in the CISA KEV catalog?

No. CVE-2026-33347 is not currently on the CISA Known Exploited Vulnerabilities list.

What is the CVSS severity of CVE-2026-33347?

CVE-2026-33347 has a CVSS v3 base score of 6.1 (MEDIUM).

What is the EPSS score for CVE-2026-33347?

CVE-2026-33347 has an EPSS score of 0.24% (15th percentile), estimating the probability of exploitation in the next 30 days.

How do I fix CVE-2026-33347?

Upgrade php-league-commonmark on debian 12 to 2.3.9-1+deb12u1 or later. Fixes are available for 2 affected products.

CVE & CISA-KEV Catalog

CVE-2026-33347

MEDIUM

6.1

CVSS v3

NVD

Description

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.

CWE-79Cross-Site Scripting (XSS)CWE-185 CWE-918Server-Side Request Forgery (SSRF)

How to fix

Remediation Available

php-league-commonmarkDebian

Fixed in:2.3.9-1+deb12u1CVE-2026-33347

Fixed in:2.7.0-1+deb13u1CVE-2026-33347

Fixed in:2.8.2-1CVE-2026-33347

php-league-commonmarkUbuntu

Fixed in:1.3.1-1ubuntu2+esm1USN-8194-1

Fixed in:1.6.7-1ubuntu0.1~esm1USN-8194-1

Fixed in:2.4.2-2ubuntu0.1~esm1USN-8194-1

Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.

CVSS v3 Vector

Exploitability

Attack VectorNetwork

Attack ComplexityLow

Privileges RequiredNone

User InteractionRequired

ScopeChanged

Impact

ConfidentialityLow

IntegrityLow

AvailabilityNone

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

Exploit Intelligence

0.24%probability of exploitation in 30 days

15thpercentile

Low risk: more likely to be exploited than 15% of all known CVEs.

References

Patch1

github.com

Vendor Advisory1

github.com

Release Notes1

github.com

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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-04-08.