Critical Vulnerabilities Exposed Nuki Smart Locks to a Plethora of Attack Options

****Researchers have identified as many as eleven critical vulnerabilities in different versions of Nuki Smart Locks.****

The IT security researchers at Manchester, England-based NCC Group have released a technical advisory explaining how Nuki Smart Locks were vulnerable to a plethora of attack possibilities.

It is worth noting that Nuki Home Solutions is a Graz, Austria-based supplier of smart home solutions in Europe. Here is a detailed overview of the eleven flaws in Nuki’s locks.

Lack of Certificate Validation on TLS Communications

This flaw is tracked as CVE-2022-32509 and affects Nuki Smart Lock version 3.0. As per the NCC Group research, the company didn’t implement SSL/TLS certificate validation on its Smart lock and Bridge devices. Without SSL/TLS certificate validation, attackers can perform man-in-the-middle attacks and access network traffic sent through an encrypted channel.

Stack Buffer Overflow Parsing JSON Responses

Tracked as CVE-2022-32504, this vulnerability affects Nuki Smart Lock 3.0. The issue can allow an attacker to get arbitrary code execution privilege on the device. The flaw is found in the code that implements the JSON objects parsing received from the SSE WebSocket, leading to a stack buffer overflow.

Stack Buffer Overflow Parsing HTTP Parameters

As per NCC Group’s technical writeup, the code responsible for overseeing the HTTP API parameter parsing logic causes a stack buffer overflow. It could be exploited to perform arbitrary code execution. This flaw is tracked as CVE-2022-32502 and was discovered in Nuki Bridge version 1.

Broken Access Controls in the BLE Protocol

The flaw is tracked as CVE-2022-32507 and affects Nuki Smart Lock 3.0. Research revealed that inadequate access control measures were used in the Bluetooth Low Energy Nuki API implementation, which could allow users to send out high-privilege commands to the Keyturner without being authorized for it.

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TAG Exposed via Test Points

This flaw is classified as CVE-2022-32503 and impacts Nuki Keypad. The TAG Exposed issue exposed the JTAG hardware interfaces on the affected devices.

Exploiting this flaw can allow an attacker to use the JTAG boundary scan feature to control code execution on the processor, debug the firmware, and read/alter the internal/external flash memory content. However, the attacker must have physical access to the circuit board to exploit the scan feature.

Sensitive Information Sent Over an Unencrypted Channel

This vulnerability is assigned CVE-2022-32510 and impacts Nuki Bridge version 1. The Bridge exposes the HTTP API using an unencrypted channel to access an administrative interface. The attacker can passively gather communication between the HTTP API and a client after accessing any device connected to the local network. A malicious actor can conveniently impersonate a legit user and access the full set of API endpoints.

WD Interfaces Exposed via Test Points

Tracked as CVE-2022-32506, the flaw exposed SWD hardware interfaces and was identified in Nuki smart lock 3.0. The attacker can use the SWD debug feature after having physical access to the circuit board, control the processor’s code execution, and debug the firmware.

SWD test points exposed (Image: Ncc Group)

Denial of Service via Unauthenticated HTTP API Messages

This flaw is classified as CVE-2022-32508 and impacts Nuki Bridge version 1. The flaw made devices vulnerable to denial of service (DoS) attacks if the attacker used specially crafted HTTP packets. Thus, impacting access to the Bridge and rendering the device unstable.

Denial of Service via Unauthenticated BLE packets

Tracked as CVE-2022-32505, this flaw made the impacted devices vulnerable to DoS attack through specially crafted Bluetooth Low energy packets. This could affect Keyturner’s availability and make the device unstable. Most BLE characteristics were found to be vulnerable to this issue.

Insecure Invite Keys Implementation

This flaw impacts the Nuki Smart Lock app version 2.22.5.5 (661). The invite token created for identifying a user during an invitation process is used to encrypt/decrypt the invite keys on the Nuki servers. A threat actor can easily take full control of the servers through this flaw and leak sensitive data.

Opener Name Could Be Overwritten Without Authentication

The Nuki Opener is impacted by this vulnerability that emerged from an insecure Opener Bluetooth Low energy implementation, allowing malicious actors to change the BLE device name. The device allowed an unauthenticated attacker to change the BLE device name.

Current status

The NCC Group informed Nuki about these flaws on 20th April 2022, and the company quickly responded. On 6th May 2022, Nuki contacted NCC Group regarding the progress on fixes. On 9th June 2022, patches were released for all vulnerabilities, after which NCC Group released a technical advisory.