← Vulnerability feed

Vulnerability record · CVE-2026-33347 · published 24 March 2026

CVE-2026-33347: Thephpleague commonmark cross-site scripting vulnerability

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.

6.3 CVSS 4.0 Medium EPSS 0.32% · top 77.9% CWE-79 · Cross-site scriptingCWE-185 · CWE-185
6.3CVSS 4.0 base score
0.32%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
3References
17 Jun 2026Last modified by 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.

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:

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://github.com/thephpleague/commonmark/commit/59fb075d2101740c337c7216e3f32b36c204218b Patch
https://github.com/thephpleague/commonmark/releases/tag/2.8.2 ProductRelease Notes
https://github.com/thephpleague/commonmark/security/advisories/GHSA-hh8v-hgvp-g3f5 MitigationVendor Advisory

Track CVE-2026-33347 inside VULONE

Watch it alongside the ransomware crews, C2 infrastructure and forum chatter that reference it, query it through the API and pull it into your SIEM over TAXII.

Start free Open in platform

Related vulnerabilities

Same products first, then exploited flaws of the same weakness class.

8.7CVE-2026-86428Thephpleague commonmark vulnerabilitycommonmark versions from 1.5.0 before 2.10.0 contain a denial of service vulnerability in the AttributesExtension when processing distinctly-named at…EPSS 0.49%8.7CVE-2026-86429Thephpleague commonmark vulnerabilityThe league/commonmark (thephpleague/commonmark) library in versions >= 1.5.0 and < 2.9.1 contains quadratic parsing complexity in its SmartPunctExten…EPSS 0.52%8.7CVE-2026-86430Thephpleague commonmark vulnerabilityleague/commonmark versions before 2.9.1 contain multiple denial of service vulnerabilities in fenced code block detection, reference link label looku…EPSS 0.49%6.9CVE-2026-86431Thephpleague commonmark cross-site scripting vulnerabilityleague/commonmark (thephpleague/commonmark) versions >= 2.7.0 and < 2.9.1 contain a cross-site scripting vulnerability in the AttributesExtension. Pr…EPSS 0.39%6.1CVE-2019-10010Thephpleague commonmark cross-site scripting vulnerabilityCross-site scripting (XSS) vulnerability in the PHP League CommonMark library before 0.18.3 allows remote attackers to insert unsafe links into HTML …EPSS 1.1%6.1CVE-2018-20583Thephpleague commonmark cross-site scripting vulnerabilityCross-site scripting (XSS) vulnerability in the PHP League CommonMark library versions 0.15.6 through 0.18.x before 0.18.1 allows remote attackers to…EPSS 1.6%5.1CVE-2026-30838Thephpleague commonmark cross-site scripting vulnerabilityleague/commonmark is a PHP Markdown parser. Prior to version 2.8.1, the DisallowedRawHtml extension can be bypassed by inserting a newline, tab, or o…EPSS 0.24%6.1CVE-2026-42897Microsoft Exchange Server XSS enables spoofingMicrosoft Exchange Server and Exchange Server Subscription Edition fail to neutralize input during web page generation, a cross-site scripting flaw (…KEVEPSS 0.52%analysed

Source: NIST National Vulnerability Database (record CVE-2026-33347), CISA KEV, FIRST EPSS (scores of 2026-09-27). This page is refreshed as NVD updates the record.