CVE-2025-32881

Executive Summary

CVE-2025-32881 exposes a critical privacy flaw in goTenna v1 devices running app version 5.5.3 and firmware 0.25.5. By default, the Group ID (GID) in messages is set to the user’s phone number unless the user explicitly opts out. Since the GID is transmitted unencrypted, an attacker within radio range can intercept messages and directly associate a phone number with a user, enabling deanonymization and potential social engineering attacks. The CVSS score of 4.3 reflects the low attack complexity and network adjacency requirement, but the impact on user privacy is significant. No public exploit code or patch is currently available.

Supply Chain & Package Security

This vulnerability is not related to NPM, PyPI, Go, or Ruby packages. It is a hardware/firmware issue in the goTenna v1 device ecosystem.

CVSS Breakdown & Threat Level

• Attack Vector (AV): Adjacent Network (AV:A) – attacker must be within radio range of the goTenna device.
• Attack Complexity (AC): Low (AC:L) – no special conditions required.
• Privileges Required (PR): None (PR:N) – no authentication needed.
• User Interaction (UI): None (UI:N) – no user action required.
• Scope (S): Unchanged (S:U) – the vulnerability does not affect other components.
• Confidentiality (C): Low (C:L) – only the GID (phone number) is exposed.
• Integrity (I): None (I:N) – no data modification.
• Availability (A): None (A:N) – no denial of service.

Threat Level: Medium. While the CVSS score is 4.3, the exposure of personally identifiable information (PII) like phone numbers elevates the risk for targeted attacks and privacy violations.

Deep Dive & Mechanics

The goTenna v1 device uses a mesh networking protocol to send messages between users. Each message includes a Group ID (GID) field that identifies the sender’s group. The vulnerability arises because:

1. Default Configuration: The GID is automatically set to the user’s phone number unless the user manually changes it in the app settings.
2. Lack of Encryption: The GID is transmitted in plaintext within the message payload. The message content may be encrypted, but the GID is not.
3. Radio Interception: An attacker with a compatible radio receiver (e.g., another goTenna device or a software-defined radio) can capture messages over the air and extract the GID.

Attack Scenario:

• An attacker positions themselves within radio range (typically up to a few miles in open terrain).
• Using a goTenna device or SDR, they capture unencrypted GID fields from messages.
• The attacker maps phone numbers to users, enabling phishing, SIM swapping, or physical tracking.

Vulnerable vs. Patched Code

Vulnerable Code (goTenna app 5.5.3 / firmware 0.25.5):

# Pseudocode illustrating the default GID assignment
def send_message(content, group_id=None):
    if group_id is None:
        group_id = user.phone_number  # Default to phone number
    packet = build_packet(content, group_id)
    radio.transmit(packet)  # GID is not encrypted

Patched Code (Hypothetical):

def send_message(content, group_id=None):
    if group_id is None:
        group_id = generate_random_gid()  # Use random identifier
    encrypted_gid = encrypt(group_id, session_key)
    packet = build_packet(content, encrypted_gid)
    radio.transmit(packet)

No official patch is available. The vendor has not released a fix.

Exploitation & Lab Setup

Red Team (Offensive)

Prerequisites:

• A goTenna v1 device with app 5.5.3 and firmware 0.25.5.
• A second goTenna device or a software-defined radio (e.g., RTL-SDR) to capture messages.
• A computer with Python and the goTenna library or custom SDR software.

Steps:

1. Set up the SDR to capture the goTenna frequency (typically 902-928 MHz ISM band).
2. Use a tool like gr-goTenna or a custom script to decode packets.
3. Extract the GID field from each packet.
4. Map GIDs to phone numbers (the GID is the phone number itself).

Example Python script (conceptual):

import radio_lib

def capture_gid():
    packet = radio_lib.receive_packet()
    gid = packet.get_field("GID")
    print(f"Captured GID: {gid}")  # This is the phone number

Blue Team (Defensive)

Detection:

• Monitor for unusual radio activity on goTenna frequencies.
• Use spectrum analyzers to detect unauthorized receivers.
• Educate users to change their GID from the default phone number.

Mitigation:

• In the goTenna app, navigate to Settings > Group ID and change it to a random string.
• Enable any available encryption options (though GID encryption is not currently supported).
• Use goTenna devices only in trusted environments.

Indicators of Compromise (IOCs)

• Network: Unencrypted GID fields in goTenna messages containing phone numbers.
• Device: goTenna v1 with app version 5.5.3 and firmware 0.25.5.
• Behavior: Repeated capture of messages from a specific goTenna device.
• File: Logs or captures containing phone numbers extracted from GID fields.

Detection Engineering

YARA Rule

rule goTenna_GID_Exposure {
    meta:
        description = "Detects goTenna messages with unencrypted GID (phone number)"
        author = "Valters IT"
        date = "2025-04-10"
        cve = "CVE-2025-32881"
    strings:
        $gid_pattern = /GID:\d{10,15}/  // Matches GID followed by 10-15 digits (phone number)
    condition:
        $gid_pattern
}

Sigma Rule

title: goTenna Unencrypted GID Detection
id: 12345678-1234-1234-1234-123456789012
status: experimental
description: Detects goTenna messages where the GID field contains a phone number (unencrypted)
author: Valters IT
date: 2025-04-10
logsource:
    category: network
    product: goTenna
detection:
    selection:
        - field: GID
          pattern: "^\d{10,15}$"
    condition: selection
falsepositives:
    - Users who intentionally set their GID to a phone number
level: medium

Suricata Rule

alert udp any any -> any any (msg:"goTenna Unencrypted GID Exposure"; content:"|47 49 44|"; offset:0; depth:3; content:"|0d 0a|"; within:20; pcre:"/GID:\d{10,15}/"; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Change Default GID: In the goTenna app, go to Settings > Group ID and set a random, non-identifying string.
2. User Awareness: Inform all users that their phone number is exposed by default and instruct them to change it.
3. Monitor for Updates: Check the goTenna website or app store for firmware/app updates that may address this issue.

Long-Term Fixes:

• The vendor should encrypt the GID field in all messages.
• Provide an option to disable the default phone number GID.
• Implement a random GID generation feature.

Workarounds:

• Use goTenna devices only in areas where radio interception is unlikely.
• Combine with VPN or other encryption for message content (though GID remains exposed).

Valters IT