CVE-2017-6900

Bash command injection in Riello NetMan 204 14-2 and 15-2 login script

• CVSS 9.8
• CWE-255
• Input Validation and Sanitization
• Remote

An issue was discovered in Riello NetMan 204 14-2 and 15-2. The issue is with the login script and wrongpass Python script used for authentication. When calling wrongpass, the variables $VAL0 and $VAL1 should be enclosed in quotes to prevent the potential for Bash command injection. Further to this, VAL0 and VAL1 should be sanitised to ensure they do not contain malicious characters. Passing it the username of '-' will cause it to time out and log the user in because of poor error handling. This will log the attacker in as an administrator where the telnet / ssh services can be enabled, and the credentials for local users can be reset. Also, login.cgi accepts the username as a GET parameter, so login can be achieved by browsing to the /cgi-bin/login.cgi?username=-%20a URI.

CVE

CVE-2017-6900

CWE

CWE-255

CVSS base score

9.8

Published

2019-07-03

OWASP

A07 Identification and Authentication Failures

Orthogonal defect classification

Function

Code defect classification

Incorrect Functionality

Category

Input Validation and Sanitization

Subcategory

Command Injection

Accessibility scope

Remote

Impact

Unauthorized Access

Solution

Secure the login.cgi script to prevent login via GET parameters.

#Proprietary, no code available

import re

def sanitize_input(username):
    # Sanitize the username to prevent malicious characters
    if re.search(r'[^a-zA-Z0-9_\-]', username):
        raise ValueError("Invalid username: contains malicious characters.")
    return username

def login(username):
    # Sanitize the username before using it
    sanitized_username = sanitize_input(username)

    # Properly quote the variables to prevent command injection
    command = f"wrongpass '{sanitized_username}'"
    
    # Execute the command safely (using subprocess, for example)
    import subprocess
    result = subprocess.run(command, shell=True, capture_output=True, text=True)

    # Check the result of the command execution
    if result.returncode == 0:
        print("Login successful.")
    else:
        print("Login failed.")

# Example usage
try:
    login('- a')  # This input should be sanitized and rejected
except ValueError as e:
    print(e)

@misc{vaitp:cve20176900,
  title        = {{Bash command injection in Riello NetMan 204 14-2 and 15-2 login script}},
  author       = {Bogaerts, Fr\'ed\'eric and Ivaki, Naghmeh and Fonseca, Jos\'e},
  year         = {2019},
  note         = {VAITP Python Vulnerability Dataset, entry CVE-2017-6900},
  howpublished = {\url{https://netpack.pt/vaitp/vulnerability/CVE-2017-6900/}}
}