Overview
CVE-2021-27289 is a significant vulnerability identified in a smart home kit developed by Ksix. The affected products include the Zigbee Gateway Module (v1.0.3), Door Sensor (v1.0.7), and Motion Sensor (v1.0.12). This vulnerability is of great concern as it exposes users to potential system compromise or data leakage, misleading users through false alerts and notifications in the mobile application designed to monitor the network.
The vulnerability stems from an improperly implemented Zigbee anti-replay mechanism, which can be exploited by attackers within wireless range. This issue underlines the increasing need for robust and secure design in IoT devices, especially with the rise in smart home technology.
Vulnerability Summary
CVE ID: CVE-2021-27289
Severity: Critical (CVSS: 9.1)
Attack Vector: Network
Privileges Required: None
User Interaction: None
Impact: Potential for system compromise, data leakage, and misleading notifications/alerts
Affected Products
No phone number, email, or personal info required.
Product | Affected Versions
Zigbee Gateway Module | v1.0.3
Door Sensor | v1.0.7
Motion Sensor | v1.0.12
How the Exploit Works
The vulnerability arises due to an incorrectly implemented anti-replay mechanism in the Zigbee protocol used in the smart home kit. This mechanism is supposed to prevent attackers from resending captured packets. However, due to the flawed implementation, an attacker within the wireless range can resend captured packets with a higher sequence number. The devices then incorrectly accept these packets as legitimate messages.
Conceptual Example Code
Below is a conceptual example of how an attacker could exploit this vulnerability:
# Import necessary libraries
from scapy.all import *
# Define the target
target = '192.168.1.100'
# Capture the packet
pkt = sniff(filter="ip and host " + target, count=1)
# Modify the frame counter field to a higher sequence number
pkt[0][ZigbeeNWK].fcf_sequence_number = 99999
# Send the modified packet
send(pkt[0], verbose=0)This pseudocode captures a packet from the targeted device and modifies the frame counter field with a higher sequence number before resending it. This leads to the devices accepting the packet as a legitimate command.
Mitigations
Ksix has released a patch to fix this vulnerability. Users should immediately update their Zigbee Gateway Module, Door Sensor, and Motion Sensor to the latest versions. As a temporary solution, using a Web Application Firewall (WAF) or Intrusion Detection System (IDS) can help prevent such replay attacks. However, the permanent solution is to update the affected devices with the provided patches.