CVE-2026-33347 Details
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.
A vulnerability exists in the Embed extension of league/commonmark, specifically in versions 2.3.0 prior to 2.8.2. The issue arises in the DomainFilteringAdapter, where a missing hostname boundary assertion in the domain-matching regex allows for an allowlist bypass. This means that an attacker-controlled domain, such as 'youtube.com.evil', can pass the allowlist check if 'youtube.com' is an allowed domain. The vulnerability has been patched in version 2.8.2.
Users can update to league/commonmark version 2.8.2, where this vulnerability has been patched. The update replaces the regex-based domain check with explicit hostname parsing using parse_url(), ensuring accurate domain matching. For those unable to update, the Embed extension can be disabled or restricted to trusted users.
Metrics
CVSS 4.0 Severity and Vector Strings:
CVSS 3.x Severity and Vector Strings:
No data available for CVSS Version 2.0 on this CVE.
CISA-ADP
Assessed Mar 26, 2026References to Advisories, Solutions, and Tools
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| URL | Source(s) | Tag(s) |
|---|---|---|
| https://github.com/thephpleague/commonmark/commit/59fb075d2101740c337c7216e3f32b36c204218b | [email protected] | Patch |
| https://github.com/thephpleague/commonmark/releases/tag/2.8.2 | [email protected] | ProductRelease Notes |
| https://github.com/thephpleague/commonmark/security/advisories/GHSA-hh8v-hgvp-g3f5 | [email protected] | MitigationVendor Advisory |
Weakness Enumeration
| CWE-ID | CWE Name | Source |
|---|---|---|
| CWE-185 | Incorrect Regular Expression | [email protected] |
| CWE-79 | Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') | [email protected] |
| CWE-918 | Server-Side Request Forgery (SSRF) | [email protected] |
Affected Products
| Product | Versions |
|---|---|
| thephpleague commonmark | >= 2.3.0, < 2.8.2 |
CPE
Remediation
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Change History
4 change records found show changes
| Date | Action | Recorded By |
|---|---|---|
| Jun 17, 2026 | CVE Modified | [email protected] |
| Jun 17, 2026 | CVE Modified | CISA-ADP |
| Apr 8, 2026 | Initial Analysis | [email protected] |
| Mar 24, 2026 | New CVE Received | [email protected] |