Is CVE-2026-33347 actively exploited?

CVE-2026-33347 has no public evidence of in-the-wild exploitation as of 2026-04-08.

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

CVE-2026-33347 has a CVSS score of 6.3 (MEDIUM severity). Vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:L/SI:L/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X.

How do I patch CVE-2026-33347?

Patch guidance is available from thephpleague security advisories. CVEDatabase generates AI-assisted remediation guidance on demand for CVE-2026-33347.

Which products are affected by CVE-2026-33347?

1 product: thephpleague commonmark.

CVE-2026-33347 - remediation guidance & executive summary

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.

CVSS Metrics

Vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:L/SI:L/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
Attack Vector: network
Complexity: low
Privileges: none
User Action: none
Confidentiality: undefined
Integrity: undefined
Availability: undefined
Weaknesses: CWE-79 · Cross-site Scripting (XSS)CWE-185 CWE-918 · Server-Side Request Forgery

Metadata

Primary Vendor: THEPHPLEAGUE
Published: 3/24/2026
Last Modified: 4/8/2026
Source: NIST NVD
Note: Verify all details with official vendor sources before applying patches.

Affected Products

thephpleague : commonmark

Remediation Guidance

Executive Summary

Cite this page

CVE-2026-33347. CVEDatabase.com. Retrieved 1 May 2026. https://cvedatabase.com/cve/CVE-2026-33347

View on NIST NVD

CVE-2026-33347 vulnerability