CVE-2026-33347 | thephpleague commonmark up to 2.8.1 PHP Markdown Parser cross site scripting (Nessus ID 303380)

VDB-352865 · CVE-2026-33347 · NESSUS 303380 THEPHPLEAGUE COMMONMARK UP TO 2.8.1 PHP MARKDOWN PARSER CROSS SITE SCRIPTING HISTORYDIFFRELATEJSONXMLCTI CVSS Meta Temp Score Current Exploit Price (≈) CTI Interest Score 4.1 $0-$5k 4.32 Summaryinfo A vulnerability identified as problematic has been detected in thephpleague commonmark up to 2.8.1. The impacted element is an unknown function of the component PHP Markdown Parser. The manipulation leads to cross site scripting. This vulnerability is referenced as CVE-2026-33347. Remote exploitation of the attack is possible. No exploit is available. You should upgrade the affected component. Detailsinfo A vulnerability, which was classified as problematic, has been found in thephpleague commonmark up to 2.8.1. This issue affects some unknown functionality of the component PHP Markdown Parser. The manipulation with an unknown input leads to a cross site scripting vulnerability. Using CWE to declare the problem leads to CWE-79. The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users. Impacted is integrity. The summary by CVE is: 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. The advisory is shared at github.com. The identification of this vulnerability is CVE-2026-33347 since 03/18/2026. The exploitation is known to be easy. The attack may be initiated remotely. No form of authentication is needed for a successful exploitation. It demands that the victim is doing some kind of user interaction. Neither technical details nor an exploit are publicly available. MITRE ATT&CK project uses the attack technique T1059.007 for this issue. The vulnerability scanner Nessus provides a plugin with the ID 303380 (Linux Distros Unpatched Vulnerability : CVE-2026-33347), which helps to determine the existence of the flaw in a target environment. Upgrading to version 2.8.2 eliminates this vulnerability. The vulnerability is also documented in the vulnerability database at Tenable (303380). Productinfo Vendor thephpleague Name commonmark Version 2.8.0 2.8.1 Website Product: https://github.com/thephpleague/commonmark/ CPE 2.3info 🔒 🔒 CPE 2.2info 🔒 🔒 CVSSv4info VulDB Vector: 🔒 VulDB Reliability: 🔍 CNA CVSS-B Score: 🔒 CNA CVSS-BT Score: 🔒 CNA Vector: 🔒 CVSSv3info VulDB Meta Base Score: 4.3 VulDB Meta Temp Score: 4.1 VulDB Base Score: 4.3 VulDB Temp Score: 4.1 VulDB Vector: 🔒 VulDB Reliability: 🔍 CVSSv2info Vector Complexity Authentication Confidentiality Integrity Availability Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock VulDB Base Score: 🔒 VulDB Temp Score: 🔒 VulDB Reliability: 🔍 Exploitinginfo Class: Cross site scripting CWE: CWE-79 / CWE-94 / CWE-74 CAPEC: 🔒 ATT&CK: 🔒 Physical: No Local: No Remote: Yes Availability: 🔒 Status: Not defined Price Prediction: 🔍 Current Price Estimation: 🔒 0-Day Unlock Unlock Unlock Unlock Today Unlock Unlock Unlock Unlock Nessus ID: 303380 Nessus Name: Linux Distros Unpatched Vulnerability : CVE-2026-33347 Threat Intelligenceinfo Interest: 🔍 Active Actors: 🔍 Active APT Groups: 🔍 Countermeasuresinfo Recommended: Upgrade Status: 🔍 0-Day Time: 🔒 Upgrade: commonmark 2.8.2 Timelineinfo 03/18/2026 CVE reserved 03/24/2026 +6 days Advisory disclosed 03/24/2026 +0 days VulDB entry created 03/24/2026 +0 days VulDB entry last update Sourcesinfo Product: github.com Advisory: github.com Status: Confirmed CVE: CVE-2026-33347 (🔒) GCVE (CVE): GCVE-0-2026-33347 GCVE (VulDB): GCVE-100-352865 Entryinfo Created: 03/24/2026 21:00 Updated: 03/24/2026 21:11 Changes: 03/24/2026 21:00 (67), 03/24/2026 21:11 (2) Complete: 🔍 Cache ID: 99:E31:101 Discussion No comments yet. Languages: en. Please log in to comment. ◂ PreviousOverviewNext ▸