CVE-2022-20946 - Cisco Firepower Threat Defense (FTD) Software GRE Tunnel Decapsulation Vulnerability

CVE-2022-20946 is a critical vulnerability found in the Generic Routing Encapsulation (GRE) tunnel decapsulation feature of Cisco Firepower Threat Defense (FTD) Software. This vulnerability leaves the system open to potential denial of service (DoS) attacks, causing affected devices to restart and lose functionality. In this post, we'll provide more details on the vulnerability, code snippets, and provide references for more information.

Vulnerability Details

The vulnerability arises from a memory handling error while processing GRE traffic. An unauthenticated, remote attacker could exploit it by sending a specially crafted GRE payload through the affected device. If the exploit is successful, the device would restart, creating a DoS condition.

Exploit Details

The exploit mainly involves crafting a malicious GRE payload and sending it through the affected device. The following code snippet demonstrates how the attack can take place:

import socket

def exploit(ip: str, port: int):
    # Create a socket
    sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)

    # Craft the malicious GRE payload
    malicious_gre_payload = b'\x00\x00\x00\x00' # fill in with the actual payload content here

    # Send the malicious GRE payload
    sock.sendto(malicious_gre_payload, (ip, port))

# Use the exploit function with the target's IP and GRE port (usually 47)
exploit("192.168.1.1", 47)

Please note that this code snippet is for informational purposes only and should not be used for malicious purposes. It is essential to follow the law and not cause harm to others.

Mitigation

It is highly recommended that users apply updates as soon as possible. Cisco has released software updates that address this vulnerability. Please refer to the following Cisco Advisory for more information on the available updates and how to apply them: Cisco Firepower Threat Defense (FTD) Software GRE Tunnel Decapsulation Vulnerability Advisory

Conclusion

In summary, CVE-2022-20946 is a critical vulnerability in the GRE tunnel decapsulation feature of Cisco FTD Software that could allow an unauthenticated, remote attacker to cause a DoS condition on an affected device. Users should apply updates as recommended by Cisco to protect their devices and networks.

References

1. Cisco Security Advisory for the Vulnerability
2. Cisco ASA, FTD, and FMC Security Advisory Bundled Publication - November 2022

Timeline

Published on: 11/15/2022 21:15:00 UTC
Last modified on: 11/22/2022 14:48:00 UTC