Summary: A vulnerability in the Simple Network Management Protocol (SNMP) service of Cisco FXOS Software for Firepower 410 Series and Firepower 930 Security Appliances and of Cisco UCS 630 Series Fabric Interconnects exposes them to denial of service attacks. The vulnerability arises from improper handling of specific SNMP requests, and an attacker can exploit this by sending a crafted SNMP request to the affected device, causing the device to reload and a denial of service condition.

A new vulnerability (CVE-2023-20200) has been discovered in the Simple Network Management Protocol (SNMP) service of specific Cisco products. This vulnerability is vital, as it affects the Cisco FXOS Software for Firepower 410 Series and Firepower 930 Security Appliances and Cisco UCS 630 Series Fabric Interconnects. An authenticated, remote attacker could exploit this vulnerability to cause a denial of service (DoS) condition on an affected device.

The root of this vulnerability lies in the improper handling of specific SNMP requests within the affected devices. An attacker can exploit this by sending a crafted SNMP request, which could, in turn, cause the device to reload, resulting in a denial of service condition.

It is important to note that this vulnerability affects all supported SNMP versions. To exploit this vulnerability through SNMPv2c or earlier, an attacker must know the SNMP community string configured on the affected device. To exploit this vulnerability through SNMPv3, the attacker must have valid credentials for an SNMP user who is configured on the affected device.

Code Snippet

#!/usr/bin/python3
import socket
import sys

# Replace TARGET_IP with the IP address of the target device
TARGET_IP = "192.168.1.1"
PORT = 161

# Replace TARGET_SNMP_COMMUNITY_STRING with SNMP community string configured on the device
TARGET_SNMP_COMMUNITY_STRING = "public"

# Crafting the malformed SNMP request
malformed_request = "ANY_NON_STANDARD_SNMP_REQUEST"

sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)

try:
    # Sending the malformed SNMP request
    sock.sendto(bytes(malformed_request, "utf-8"), (TARGET_IP, PORT))
    print("[*] Malformed SNMP request sent.")
except Exception as e:
    print("[!] Error sending request:", e)
finally:
    sock.close()

Original References:

1. Cisco Security Advisory - Cisco FXOS and UCS Fabric Interconnect Software SNMP Denial of Service Vulnerability
2. Mitigating SNMP Vulnerabilities in Cisco FXOS Software and UCS Fabric Interconnects

Exploit Details

The vulnerability (CVE-2023-20200) affects the Cisco FXOS Software for Firepower 410 Series and Firepower 930 Security Appliances and the Cisco UCS 630 Series Fabric Interconnects. The vulnerability stems from the improper processing of specific SNMP requests.

To mitigate this issue, it is highly recommended that users and administrators of affected devices follow the guidelines provided by Cisco. Users should update their software to the latest version available and follow Cisco's recommendations for their specific devices.

We would like to reiterate that this vulnerability affects all supported SNMP versions. An attacker must have knowledge of the SNMP community string (for SNMPv2c or earlier) or valid SNMP user credentials (for SNMPv3) for a successful exploit. It is essential to keep this information confidential and secure to minimize the risk of exploitation.

For more details on this vulnerability and recommended actions, please refer to the original references above. Stay vigilant, and make sure your devices are up to date.

Timeline

Published on: 08/23/2023 19:15:08 UTC
Last modified on: 09/07/2023 17:58:03 UTC