CVE-2023-7005

Executive Summary

CVE-2023-7005 is a critical vulnerability in the TTLock ecosystem, specifically affecting the TTLock mobile application and its communication with compatible smart locks. The flaw allows an attacker to send a specially crafted message that forces the encryption protocol used for communication to be downgraded to a weaker, less secure standard. This downgrade attack can then be leveraged to compromise the lock, most notably by revealing the unlockKey field, which is the secret credential required to unlock the device. The vulnerability is currently unpatched, and no official fix has been released by the vendor, Ttlock. The CVSS score is listed as 0.0, likely due to incomplete or missing scoring data, but the technical impact is severe, as it undermines the core security of the lock's authentication mechanism.

Supply Chain & Package Security

This vulnerability is not related to an open-source package (NPM, PyPI, Go, Ruby) but rather to a proprietary hardware/software ecosystem (TTLock). The supply chain risk is primarily to end-users and organizations that have deployed TTLock devices, as the vulnerability exists in the official TTLock App and its communication protocol. No patch or update is currently available, meaning all deployments are at risk.

CVSS Breakdown & Threat Level

The CVSS score is listed as 0.0, which is unusual and likely indicates that the NVD has not yet assigned a proper score. However, based on the technical description, a reasonable assessment would be:

• Attack Vector (AV): Network (the attacker can send the crafted message remotely)
• Attack Complexity (AC): Low (the attack does not require special conditions)
• Privileges Required (PR): None (no authentication needed to send the downgrade message)
• User Interaction (UI): None (the attack does not require user action)
• Scope (S): Unchanged (the vulnerable component is the lock itself)
• Confidentiality (C): High (the unlockKey is exposed)
• Integrity (I): High (the lock can be unlocked by an attacker)
• Availability (A): Low (the lock may be rendered unusable or compromised)

Estimated CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:L Estimated Score: 9.0 (Critical)

Threat Level: Critical. The vulnerability allows for remote, unauthenticated compromise of the lock's security, leading to unauthorized physical access.

Deep Dive & Mechanics

The TTLock App communicates with TTLock smart locks over Bluetooth Low Energy (BLE) or potentially other wireless protocols. The communication is encrypted to prevent eavesdropping and tampering. The vulnerability lies in the protocol negotiation phase, where the app and lock agree on which encryption algorithm to use.

An attacker can intercept or inject a specially crafted message during this negotiation phase. This message forces the lock and app to downgrade from a strong encryption protocol (e.g., AES-256) to a weaker one (e.g., AES-128 or even a custom, flawed algorithm). Once the weaker protocol is in use, the attacker can more easily decrypt the traffic or perform a man-in-the-middle attack.

The critical payload is the unlockKey field. This is a secret key stored on the lock and used by the app to authenticate and unlock the device. By downgrading the encryption, the attacker can either:

1. Directly read the unlockKey from the downgraded communication.
2. Exploit weaknesses in the downgraded protocol to derive the key.

With the unlockKey, the attacker can unlock the lock at will, bypassing any legitimate access controls.

Vulnerable vs. Patched Code

No patched code is available. The vulnerable code is within the proprietary TTLock App and firmware. The following is a conceptual representation of the vulnerable protocol negotiation:

Vulnerable (Downgrade Allowed):

# Pseudo-code for vulnerable negotiation
def negotiate_protocol(lock_version, app_version):
    if lock_version < 2.0:
        # Allow downgrade to weak protocol
        return "WEAK_PROTOCOL"
    else:
        return "STRONG_PROTOCOL"

Patched (No Downgrade):

# Pseudo-code for patched negotiation
def negotiate_protocol(lock_version, app_version):
    # Always use the strongest protocol supported by both
    return "STRONG_PROTOCOL"

The patched version would reject any attempt to downgrade the encryption, ensuring that only the strongest available protocol is used.

Exploitation & Lab Setup

Red Team (Exploitation)

Lab Setup:

1. Hardware: A TTLock smart lock (e.g., TTLock Pro) and a smartphone with the TTLock App installed.
2. Software: A BLE-capable device (e.g., Raspberry Pi with Bluetooth adapter) running a custom script to intercept and inject BLE packets.
3. Tools: btlejack, bettercap, or a custom Python script using bluepy or pygatt.

Exploitation Steps:

1. Scan for TTLock devices: Use btlejack -s to discover nearby BLE devices.
2. Identify the TTLock: Look for the device name or service UUID associated with TTLock.
3. Intercept the negotiation: Use btlejack -f <channel> -o capture.pcap to capture BLE traffic during the app-lock pairing or unlocking process.
4. Craft the downgrade message: Create a BLE packet that mimics a legitimate negotiation request but forces the use of a weak encryption protocol.
5. Inject the message: Use btlejack -i <packet> to inject the crafted packet into the communication stream.
6. Capture the unlockKey: After the downgrade, the unlockKey may be transmitted in plaintext or with weak encryption. Capture and decode it.
7. Unlock the lock: Use the captured unlockKey to send an unlock command to the lock.

Example Exploit Script (Conceptual):

import btlejack

# Connect to the TTLock
lock = btlejack.connect("TTLock_Device_Address")

# Craft a downgrade message
downgrade_packet = b"\x00\x01\x02\x03"  # Placeholder for actual downgrade command

# Inject the packet
btlejack.inject(lock, downgrade_packet)

# Capture the unlockKey
unlock_key = btlejack.capture(lock, timeout=5)
print(f"Captured unlockKey: {unlock_key}")

Blue Team (Defense)

Detection and Prevention:

1. Monitor BLE traffic: Use tools like btlejack or Wireshark to monitor for unusual BLE packets, especially those that attempt to change encryption parameters.
2. Firmware updates: Regularly check for and apply any firmware updates from TTLock. Since no patch exists, consider isolating the lock from untrusted networks.
3. Network segmentation: Place TTLock devices on a separate VLAN or network segment to limit exposure.
4. Physical security: Use additional physical locks or tamper-evident seals to detect unauthorized access.
5. Logging: Enable logging on the TTLock App and lock firmware (if available) to record all unlock attempts and protocol negotiations.

Indicators of Compromise (IOCs)

• Network IOCs:

  • BLE packets with unusual or unexpected encryption negotiation parameters.
  • Repeated connection attempts from unknown BLE devices.
  • Sudden changes in the lock's behavior (e.g., unlocking without a valid app command).

• Host IOCs:

  • The TTLock App logs showing failed or downgraded encryption negotiations.
  • Unusual BLE device names or MAC addresses in the vicinity.

• File IOCs:

  • Captured BLE traffic files (e.g., .pcap) containing downgrade messages.
  • Log files with entries like WEAK_PROTOCOL or encryption downgrade.

Detection Engineering

YARA Rule

rule TTLock_Encryption_Downgrade {
    meta:
        description = "Detects BLE packets attempting to downgrade TTLock encryption"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2023-7005"
    strings:
        $downgrade_cmd = { 00 01 02 03 }  // Placeholder for actual downgrade command bytes
        $weak_proto = "WEAK_PROTOCOL"
    condition:
        $downgrade_cmd or $weak_proto
}

Sigma Rule

title: TTLock Encryption Downgrade Attempt
id: 8a9b7c6d-5e4f-3a2b-1c0d-9e8f7a6b5c4d
status: experimental
description: Detects attempts to downgrade encryption protocol in TTLock communication
author: Valters IT
date: 2025-04-10
references:
    - CVE-2023-7005
logsource:
    category: network
    product: bluetooth
detection:
    selection:
        - event: "encryption_negotiation"
        - parameters: "WEAK_PROTOCOL"
    condition: selection
falsepositives:
    - Legitimate firmware updates that change protocol
level: high

Suricata Rule

alert tcp any any -> any any (msg:"TTLock Encryption Downgrade Attempt"; content:"|00 01 02 03|"; sid:1000001; rev:1; reference:cve,2023-7005;)

Remediation & Mitigation

Immediate Actions:

1. Disable remote access: If the TTLock App supports remote unlocking via a cloud service, disable this feature until a patch is available.
2. Use physical keys: Rely on the physical key override (if available) instead of the app for critical access.
3. Monitor BLE traffic: Use BLE monitoring tools to detect any suspicious activity around the lock.

Long-term Solutions:

1. Vendor patch: Contact Ttlock and demand a firmware/app update that prevents encryption downgrade.
2. Replace hardware: If no patch is forthcoming, consider replacing the TTLock with a more secure alternative.
3. Network controls: Implement BLE firewalls or intrusion detection systems that can block malicious BLE packets.

Valters IT Signature This report was generated by Valters IT DevSecOps AI. For questions, contact security@valters-it.com.